fix: replace unicode characters and fix finalize-restore endpoint

Style check fixes:
- Replace unicode box-drawing characters with ASCII (|-- instead of ├──)
- Replace emoji status markers with [OK]/[FAIL]/[WARN] tags
- Replace arrows (→ with ->, ↔ with <->) and em-dashes (— with --)
- Add venv-quick to excluded directories in check script
- Exclude darkwing report files (findings.sarif, report.md)

Backup finalization fix:
- Fix finalize-restore endpoint to not claim the upgrade sentinel
- Endpoint now checks for pending upgrade and returns {queued: true}
- Leaves UPGRADE_SENTINEL for background watcher to claim and process
- Prevents inline Alembic runs that can outlast request timeout

Claude Code context:
- Add .claude/ directory with INDEX.md and QUICK-REFERENCE.md
- Add CLAUDE.md with project overview and conventions
- Helps Claude Code understand project structure and rules

Fixes failing test: test_the_endpoint_does_not_run_the_upgrade_itself
Fixes naming/style CI check violations

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

agent/QUICK-FIX-VM.md

@@ -33,10 +33,10 @@ cd C:\ProgramData\ShopDB\EndpointAgent
 
 ## Why HTTP is OK Here
 
-- ✅ VM and host on same physical machine (Hyper-V)
-- ✅ Traffic never leaves the host
-- ✅ Hyper-V internal network is isolated
-- ✅ No external network exposure
+- [X] VM and host on same physical machine (Hyper-V)
+- [X] Traffic never leaves the host
+- [X] Hyper-V internal network is isolated
+- [X] No external network exposure
 
 For production multi-machine deployment, use HTTPS with proper certificates.