Fix icon extraction, drop overlay styling, and card padding

- Fix upsert_appimage returning 0 for existing records by falling
  back to a SELECT query when last_insert_rowid is 0
- Replace --appimage-offset execution with binary squashfs magic scan
  to avoid hanging on AppImages with custom AppRun scripts
- Add 5-second timeout fallback if binary scan fails
- Extract desktop files from usr/share/applications/ for reverse-DNS
  named entries that root-level *.desktop glob misses
- Add root-level png/svg fallback in icon search
- Add CSS for drop overlay scrim, drop zone card, and drop zone icon
- Add card padding (24px 20px) so content does not touch card edges
- Always scan on startup to discover new AppImages

src/window.rs

@@ -784,11 +784,8 @@ impl DriftwoodWindow {
             }
         }
 
-        // Auto-scan on startup if enabled
-        let settings = self.settings();
-        if settings.boolean("auto-scan-on-startup") {
-            self.trigger_scan();
-        }
+        // Always scan on startup to discover new AppImages and complete pending analyses
+        self.trigger_scan();
 
         // Check for orphaned desktop entries in the background
         let toast_overlay = self.imp().toast_overlay.get().unwrap().clone();
@@ -878,7 +875,8 @@ impl DriftwoodWindow {
                         let size_unchanged = ex.size_bytes == d.size_bytes as i64;
                         let mtime_unchanged = modified.as_deref() == ex.file_modified.as_deref();
                         let analysis_done = ex.analysis_status.as_deref() == Some("complete");
-                        if size_unchanged && mtime_unchanged && analysis_done {
+                        let has_icon = ex.icon_path.is_some();
+                        if size_unchanged && mtime_unchanged && analysis_done && has_icon {
                             skipped_count += 1;
                             continue;
                         }