Add Phase 5 enhancements: security, i18n, analysis, backup, notifications

- Database v8 migration: tags, pinned, avg_startup_ms columns
- Security scanning with CVE matching and batch scan
- Bundled library extraction and vulnerability reports
- Desktop notification system for security alerts
- Backup/restore system for AppImage configurations
- i18n framework with gettext support
- Runtime analysis and Wayland compatibility detection
- AppStream metadata and Flatpak-style build support
- File watcher module for live directory monitoring
- Preferences panel with GSettings integration
- CLI interface for headless operation
- Detail view: tabbed layout with ViewSwitcher in title bar,
  health score, sandbox controls, changelog links
- Library view: sort dropdown, context menu enhancements
- Dashboard: system status, disk usage, launch history
- Security report page with scan and export
- Packaging: meson build, PKGBUILD, metainfo

docs/plans/2026-02-27-20-improvements.md

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+# 20 Improvements Plan
+
+## Batch 1: Low-risk code quality (no behavior change)
+1. Wrap all hardcoded English strings in i18n()
+2. Replace OnceCell.get().expect() with safe getters
+3. Extract common async-toast-refresh helper
+4. Log silently swallowed errors
+
+## Batch 2: Performance
+6. Async database initialization with loading screen
+7. Batch CSS provider registration for letter-circle icons
+8. Lazy-load detail view tabs
+18. Rate-limit background analysis spawns
+
+## Batch 3: UX
+9. Progress indicator during background analysis
+10. Multi-file drop and file picker support
+12. Sort options in library view
+15. Keyboard shortcut Ctrl+O for Add app
+17. Validate scan directories exist before scanning
+
+## Batch 4: Robustness
+5. Add database migration tests
+13. Confirmation before closing during active analysis
+16. Graceful handling of corrupt/locked database
+
+## Batch 5: Accessibility & Features
+11. Remember detail view active tab
+14. Announce analysis completion to screen readers
+19. Custom launch arguments
+20. Export/import app library