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

build.rs

@@ -33,4 +33,12 @@ fn main() {
         "cargo::rustc-env=GSETTINGS_SCHEMA_DIR={}",
         schema_dir.display()
     );
+
+    // Set LOCALEDIR for i18n support (development builds use a local path)
+    let locale_dir = out_dir.join("locale");
+    std::fs::create_dir_all(&locale_dir).ok();
+    println!(
+        "cargo::rustc-env=LOCALEDIR={}",
+        locale_dir.display()
+    );
 }