feat(nodes): agent self-upgrade (#57)

POST /agents/:id/upgrade enqueues a self_upgrade command carrying the
target platform, the sha256 the server computed over its bundled binary,
and the server version. The agent downloads the replacement from the
existing /api/agents/download/:platform endpoint, verifies the checksum,
sanity-checks the new binary (--version), atomically swaps its own
executable, reports the command result, then re-execs via syscall.Exec —
no supervisor or restart plumbing required.

Agents stamp main.version via ldflags at image build, expose --version,
and now send version at register so node_agents.version refreshes on
re-register (older agents without the field keep their stored value).
The server rejects upgrades for offline nodes and for platforms with no
bundled binary (linux-amd64/linux-arm64 ship in the image).

Surfaces: nodes upgrade CLI, containr_nodes_upgrade MCP (confirm-gated),
node-detail page button, OpenAPI. Verified live: v0.0.3 agent upgraded
to v0.0.4 in place, re-registered with the new version; offline node
returns 409 NODE_OFFLINE.

Generated with [Devin](https://devin.ai)

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/frontend/src/generated/docs-snapshot.ts

@@ -40,7 +40,7 @@ export const bundledDocs: BundledDoc[] = [
     "path": "guides/CLI.md",
     "section": "guides",
     "title": "Containr CLI",
-    "markdown": "# Containr CLI\n\nThe CLI controls every part of a Containr instance — the same API surface\nthe web UI uses. Build it with `scripts/build-cli.sh` or\n`go build ./cmd/cli` from `app/backend`.\n\n## Authentication\n\nCreate a personal access token in the web UI under\n**Settings → Personal Access Tokens** (or `containr tokens create`), then:\n\n```bash\ncontainr auth login cnp_...                      # verify + store\ncontainr auth login cnp_... --url https://containr.example.com\ncontainr auth login cnp_... --name production    # named profile\ncontainr auth status                             # show active profile + identity\ncontainr auth logout\n```\n\nResolution order for every command: `--token`/`--api-url` flags >\n`CONTAINR_TOKEN`/`CONTAINR_API_URL` env > active profile >\n`http://localhost:8080/api/v1`. The active profile is `--profile` >\n`CONTAINR_PROFILE` > `current_profile` in `~/.containr.yaml`.\n\n## Output and scripting\n\n- `--json` prints the raw API response — safe to pipe and parse.\n- `--yes` / `-y` skips confirmation on destructive commands (delete,\n  revoke, restore, failover). Non-interactive shells refuse destructive\n  commands without it.\n- Exit codes are stable: `0` ok, `1` error, `2` auth/permission,\n  `3` not found, `4` validation, `5` unreachable.\n\n## Commands\n\n```\nauth login|logout|status         token auth and profiles\ntokens list|create|revoke        personal access tokens\nprojects list|get|create|delete\nservices list|get|create|update|delete|start|stop|restart|redeploy\nservices clone|move              duplicate config or re-parent a service\nservices domains list|add|remove|default|check   multi-domain + DNS preflight\nregistries list|add|update|remove  private-image pull credentials\nvolumes list|delete              docker volume inventory + cleanup (admin)\ndeploy <service-id>              trigger a deployment (--no-cache, --commit-hash, --branch)\ndeployments list|get|logs|rollback|cancel\nlogs <service-id> [--follow]     runtime logs (SSE follow)\nexec <service-id> -- <cmd>       one-off container command\nvariables list|set|unset         env vars (secrets masked; --redeploy applies them)\nvariables shared list|set|unset  project shared vars — referenced as ${{shared.KEY}}\ndatabases list|get|create|update|delete|action|backup|restore|download-backup|import-backup\n                               import-backup <id> <file.tar.gz|-> uploads an archive as a restore\n                               point; ships offsite too when a backup target is assigned\ndatabases list|get|create|update|delete|action|backup|restore|download-backup\n                               create --public exposes the port on all interfaces;\n                               update <id> --public/--public=false toggles it (container recreates, data persists)\ndatabases register <name>      register an external database (--type --host --port --database --username --password --ssl; probed before storing)\ndatabases test-connection      probe a connection — by id, or ad-hoc flags\nbackup-targets list|add|update|remove|test\n                               S3-compatible archive destinations; add/update probe the bucket\n                               first, empty --access-key/--secret-key on update keep stored keys;\n                               update <db-id> --backup-target assigns a target (\"\" clears it)\ncron list|get|create|delete|trigger|executions\ntemplates list|get|create|delete|deploy|plan|import-compose|deploy-graph\n                               deploy --name --var K=V; plan dry-resolves expressions;\n                               import-compose <compose.yml|-> converts a compose file into\n                               a v2 graph config; deploy-graph <project-id> <config.json|->\n                               deploys an ad-hoc service graph\nimport compose <project-id> <compose.yml|->\n                               deploys a docker-compose file straight into a project —\n                               no template row. DB images become managed databases\n                               attached under their service name; --var K=V overrides\n                               template variables\nnodes list|get|delete|tokens     node agents + onboarding tokens (admin)\nnodes add <user@host>            SSH bootstrap — one session installs the agent, then never needed again (--print for manual runs)\nnodes update|prune|commands      rename/auto-prune, bounded docker prune, command history\nmigrate railway                  pull a Railway project (services, vars, domains) via GraphQL and recreate it — --dry-run prints the plan\nmigrate dflow                    import a dflow project (services, vars, volumes, domains) via its Payload REST API — needs --url + --api-key, --dry-run prints the plan\nscaling status|policies|services|scale\nha status|alerts|health|policies|enable|disable|failover\nsecurity scan|vulnerabilities|metrics\ngateway services|keys|anLine truncated
+    "markdown": "# Containr CLI\n\nThe CLI controls every part of a Containr instance — the same API surface\nthe web UI uses. Build it with `scripts/build-cli.sh` or\n`go build ./cmd/cli` from `app/backend`.\n\n## Authentication\n\nCreate a personal access token in the web UI under\n**Settings → Personal Access Tokens** (or `containr tokens create`), then:\n\n```bash\ncontainr auth login cnp_...                      # verify + store\ncontainr auth login cnp_... --url https://containr.example.com\ncontainr auth login cnp_... --name production    # named profile\ncontainr auth status                             # show active profile + identity\ncontainr auth logout\n```\n\nResolution order for every command: `--token`/`--api-url` flags >\n`CONTAINR_TOKEN`/`CONTAINR_API_URL` env > active profile >\n`http://localhost:8080/api/v1`. The active profile is `--profile` >\n`CONTAINR_PROFILE` > `current_profile` in `~/.containr.yaml`.\n\n## Output and scripting\n\n- `--json` prints the raw API response — safe to pipe and parse.\n- `--yes` / `-y` skips confirmation on destructive commands (delete,\n  revoke, restore, failover). Non-interactive shells refuse destructive\n  commands without it.\n- Exit codes are stable: `0` ok, `1` error, `2` auth/permission,\n  `3` not found, `4` validation, `5` unreachable.\n\n## Commands\n\n```\nauth login|logout|status         token auth and profiles\ntokens list|create|revoke        personal access tokens\nprojects list|get|create|delete\nservices list|get|create|update|delete|start|stop|restart|redeploy\nservices clone|move              duplicate config or re-parent a service\nservices domains list|add|remove|default|check   multi-domain + DNS preflight\nregistries list|add|update|remove  private-image pull credentials\nvolumes list|delete              docker volume inventory + cleanup (admin)\ndeploy <service-id>              trigger a deployment (--no-cache, --commit-hash, --branch)\ndeployments list|get|logs|rollback|cancel\nlogs <service-id> [--follow]     runtime logs (SSE follow)\nexec <service-id> -- <cmd>       one-off container command\nvariables list|set|unset         env vars (secrets masked; --redeploy applies them)\nvariables shared list|set|unset  project shared vars — referenced as ${{shared.KEY}}\ndatabases list|get|create|update|delete|action|backup|restore|download-backup|import-backup\n                               import-backup <id> <file.tar.gz|-> uploads an archive as a restore\n                               point; ships offsite too when a backup target is assigned\ndatabases list|get|create|update|delete|action|backup|restore|download-backup\n                               create --public exposes the port on all interfaces;\n                               update <id> --public/--public=false toggles it (container recreates, data persists)\ndatabases register <name>      register an external database (--type --host --port --database --username --password --ssl; probed before storing)\ndatabases test-connection      probe a connection — by id, or ad-hoc flags\nbackup-targets list|add|update|remove|test\n                               S3-compatible archive destinations; add/update probe the bucket\n                               first, empty --access-key/--secret-key on update keep stored keys;\n                               update <db-id> --backup-target assigns a target (\"\" clears it)\ncron list|get|create|delete|trigger|executions\ntemplates list|get|create|delete|deploy|plan|import-compose|deploy-graph\n                               deploy --name --var K=V; plan dry-resolves expressions;\n                               import-compose <compose.yml|-> converts a compose file into\n                               a v2 graph config; deploy-graph <project-id> <config.json|->\n                               deploys an ad-hoc service graph\nimport compose <project-id> <compose.yml|->\n                               deploys a docker-compose file straight into a project —\n                               no template row. DB images become managed databases\n                               attached under their service name; --var K=V overrides\n                               template variables\nnodes list|get|delete|tokens     node agents + onboarding tokens (admin)\nnodes add <user@host>            SSH bootstrap — one session installs the agent, then never needed again (--print for manual runs)\nnodes update|prune|commands      rename/auto-prune, bounded docker prune, command history\nmigrate railway                  pull a Railway project (services, vars, domains) via GraphQL and recreate it — --dry-run prints the plan\nmigrate dflow                    import a dflow project (services, vars, volumes, domains) via its Payload REST API — needs --url + --api-key, --dry-run prints the plan\nscaling status|policies|services|scale\nha status|alerts|health|policies|enable|disable|failover\nsecurity scan|vulnerabilities|metrics\ngateway services|keys|anLine truncated
   },
   {
     "path": "guides/CLOUDFLARE_SETUP.md",