feat(nodes): SSH bootstrap + housekeeping — install script, bundled binaries, auto-prune (#50)

* feat(nodes): SSH bootstrap + housekeeping — install script, bundled binaries, auto-prune

- `containr nodes add <user@host>` mints an enroll token, SSHes once,
  runs the install script remotely; --print emits the one-liner
- Public /api/agents/install.sh + /api/agents/download/{platform};
  agent binaries built into the image under /agents
- Agent-side `prune` (bounded docker system prune, volumes opt-in)
  and `system_df` commands
- node_agents.auto_prune + health sweep enqueues daily prune;
  offline/online transitions notify admins
- CLI nodes update/prune/commands + MCP tools (prune confirm-gated)
- Usage page: install one-liner, per-node Prune + auto toggle

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

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

* feat(nodes): node detail page — telemetry, containers, commands, controls

/nodes/:id (admin): cpu/mem sparklines from heartbeat history
(1h/24h/7d), containers on node, command history, inline rename,
auto-prune toggle, prune-now with volume opt-in, remove. Agent rows
on the Usage page link into it.

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

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

* feat(nodes): mesh awareness + node detail page

- agent reports tailscale/netbird/zerotier/wireguard interface IPs at
  register (authoritative — absent interfaces clear stored state)
- backend stores under node_agents.metadata.mesh, merged on re-register
- node detail page shows mesh addresses under the primary IP

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

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

---------

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

app/backend/Dockerfile

@@ -13,6 +13,10 @@ ARG VERSION=dev
 RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo \
     -ldflags "-X containr/internal/api.Version=${VERSION}" -o main cmd/server/main.go
 
+# Node-agent binaries served by the API for SSH/bootstrap installs.
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o /agents/containr-agent-linux-amd64 ./cmd/agent && \
+    CGO_ENABLED=0 GOOS=linux GOARCH=arm64 go build -o /agents/containr-agent-linux-arm64 ./cmd/agent
+
 # Build embedded Better Auth runtime dependencies
 FROM node:22-alpine AS auth-builder
 
@@ -35,6 +39,7 @@ WORKDIR /app
 
 COPY --from=go-builder /app/main ./main
 COPY --from=go-builder /app/migrations_goose ./migrations_goose
+COPY --from=go-builder /agents /agents
 COPY --from=auth-builder /auth ./auth
 
 RUN chown -R appuser:appgroup /app