feat(cli): v2 — full API coverage, profiles, --json/--yes, containr up

Rewrite the CLI as a thin client over the authenticated API so agents
and scripts reach every resource the UI does (ROADMAP2 phase A2).

- shared Client with bearer auth, error-envelope decoding, and stable
  exit codes: 0 ok / 1 error / 2 auth / 3 not-found / 4 validation /
  5 unreachable
- named profiles in ~/.containr.yaml (current_profile + profiles.*);
  resolution order --flag > env > profile > localhost default;
  CONTAINR_TOKEN / CONTAINR_API_URL / CONTAINR_PROFILE env support
- --json prints raw API responses; --yes skips confirmations;
  destructive commands refuse non-interactively without it
- auth login verifies the token against /user/profile before saving,
  interactive prompt via term.ReadPassword
- commands for every resource: tokens, projects, services, deploy,
  deployments (logs/rollback), logs --follow (SSE), exec, variables
  (set/unset merge with secret masking preserved), databases
  (backup/restore/download), cron, templates, nodes + agent tokens,
  scaling, ha, security, gateway, admin, notifications
- containr up: git remote + branch → create-or-reuse service → deploy

Verified live: login/status/tokens/projects/services, up creating a
service + deployment, non-TTY confirmation refusal, scope-capped admin
rejection (exit 2), revoke.

Authored By: TDvorak <[email protected]>

app/backend/go.mod

@@ -86,6 +86,7 @@ require (
 	golang.org/x/net v0.59.0 // indirect
 	golang.org/x/sync v0.23.0 // indirect
 	golang.org/x/sys v0.48.0 // indirect
+	golang.org/x/term v0.46.0 // indirect
 	golang.org/x/text v0.42.0 // indirect
 	golang.org/x/time v0.11.0 // indirect
 	golang.org/x/tools v0.49.0 // indirect