Implement Driftwood AppImage manager - Phases 1 and 2

Phase 1 - Application scaffolding:
- GTK4/libadwaita application window with AdwNavigationView
- GSettings-backed window state persistence
- GResource-compiled CSS and schema
- Library view with grid/list toggle, search, sorting, filtering
- Detail view with file info, desktop integration controls
- Preferences window with scan directories, theme, behavior settings
- CLI with list, scan, integrate, remove, clean, inspect commands
- AppImage discovery, metadata extraction, desktop integration
- Orphaned desktop entry detection and cleanup
- AppImage packaging script

Phase 2 - Intelligence layer:
- Database schema v2 with migration for status tracking columns
- FUSE detection engine (libfuse2/3, fusermount, /dev/fuse, AppImageLauncher)
- Wayland awareness engine (session type, toolkit detection, XWayland)
- Update info parsing from AppImage ELF sections (.upd_info)
- GitHub/GitLab Releases API integration for update checking
- Update download with progress tracking and atomic apply
- Launch wrapper with FUSE auto-detection and usage tracking
- Duplicate and multi-version detection with recommendations
- Dashboard with system health, library stats, disk usage
- Update check dialog (single and batch)
- Duplicate resolution dialog
- Status badges on library cards and detail view
- Extended CLI: status, check-updates, duplicates, launch commands

49 tests passing across all modules.

src/ui/widgets.rs

@@ -0,0 +1,24 @@
+use gtk::prelude::*;
+
+/// Create a status badge pill label with the given text and style class.
+/// Style classes: "success", "warning", "error", "info", "neutral"
+pub fn status_badge(text: &str, style_class: &str) -> gtk::Label {
+    let label = gtk::Label::new(Some(text));
+    label.add_css_class("status-badge");
+    label.add_css_class(style_class);
+    label
+}
+
+/// Create a badge showing integration status.
+pub fn integration_badge(integrated: bool) -> gtk::Label {
+    if integrated {
+        status_badge("Integrated", "success")
+    } else {
+        status_badge("Not integrated", "neutral")
+    }
+}
+
+/// Format bytes into a human-readable string.
+pub fn format_size(bytes: i64) -> String {
+    humansize::format_size(bytes as u64, humansize::BINARY)
+}