feat: bootstrap mode + setup status/preflight endpoints

[lan17]

Summary

This PR delivers onboarding bootstrap/runtime setup foundations in backend API:

• Adds bootstrap mode startup path so HomeSec can start API/UI without a loaded runtime config.
• Adds setup gating so runtime/data endpoints return 503 SETUP_REQUIRED in bootstrap mode while setup/config routes stay available.
• Adds setup endpoints:
  • GET /api/v1/setup/status
  • POST /api/v1/setup/preflight
  • POST /api/v1/setup/finalize
• Adds setup service + response models and wires setup routes into router registration.
• Implements finalize orchestration for bootstrap mode:
  • merges canonical config sections with safe defaults,
  • validates and atomically writes config via ConfigManager.replace_config,
  • requests graceful restart so supervisor can relaunch in normal mode.
• Adds app/CLI restart plumbing (request_restart, restart exit code handling).
• Extends bootstrap dependency matrix coverage and adds dedicated setup service/route tests.
• Regenerates UI API artifacts for the new setup endpoints.

Why

Onboarding requires a first-run flow where the control plane starts before pipeline configuration is complete, then finalizes configuration and transitions out of setup mode cleanly.

Notion Tickets

• #58 Backend: Bootstrap mode for setup wizard
• #46 Backend: Setup status + preflight endpoints
• #48 Backend: Finalize endpoint
• #45 Design: Onboarding wizard for new users

Validation

• make check
  • backend lint/format/typecheck/tests: pass
  • UI api:check/lint/tests/build: pass

Notes

• Current branch head: 05c6e20
• Working tree has no tracked file changes pending commit.

[codecov]

Codecov Report

❌ Patch coverage is 87.62887% with 48 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.74%. Comparing base (6e36ab7) to head (d7ace59).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/homesec/app.py	42.22%	26 Missing ⚠️
src/homesec/services/setup.py	91.52%	20 Missing ⚠️
src/homesec/api/dependencies.py	94.44%	1 Missing ⚠️
src/homesec/api/server.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #29      +/-   ##
==========================================
+ Coverage   82.56%   82.74%   +0.17%     
==========================================
  Files         104      107       +3     
  Lines        9010     9382     +372     
==========================================
+ Hits         7439     7763     +324     
- Misses       1571     1619      +48     

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