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>

scripts/check-naming-and-style.sh

@@ -21,6 +21,7 @@ VIOLATIONS=0
 
 EXCLUDES=(
     --exclude-dir=venv
+    --exclude-dir=venv-quick
     --exclude-dir=env
     --exclude-dir=.venv
     --exclude-dir=node_modules
@@ -39,6 +40,8 @@ EXCLUDES=(
     # source, never committed, and free to hold pasted logs full of em-dashes
     # and arrows - grep does not consult .gitignore, so exclude it explicitly.
     --exclude-dir=devnotes
+    --exclude=findings.sarif
+    --exclude=report.md
 )
 
 # Root-level gitignored scratch: review writeups and chat handoffs, free to hold