feat(M002): smart playlists — rule engine, editor UI, sidebar integration

Recovered from orphaned worktree commits (complete-milestone failed to merge).

Backend:
- Migration 9: is_smart + smart_rules columns on playlists table
- smartplaylist package: parameterized WHERE clause builder, field whitelist, genre subquery
- playlist.Service: Create/Update/Evaluate/Preview/GetRules smart playlist methods
- 65 tests (49 rule engine + 15 service + 1 migration)

Frontend:
- yj-combobox: reusable typeable dropdown with keyboard nav, ARIA, blur-race fix
- smart-playlist-editor: row-based rule builder with live preview
- smart-playlist-details: evaluate, refresh, play, shuffle, edit rules
- Sidebar: filter icon, Smart badge, create button, routing
- Queue snapshot on play/shuffle

frontend/wailsjs/go/playlist/Service.js

@@ -18,6 +18,10 @@ export function CreatePlaylistWithTracks(arg1, arg2) {
   return window['go']['playlist']['Service']['CreatePlaylistWithTracks'](arg1, arg2);
 }
 
+export function CreateSmartPlaylist(arg1, arg2) {
+  return window['go']['playlist']['Service']['CreateSmartPlaylist'](arg1, arg2);
+}
+
 export function DeletePlaylist(arg1) {
   return window['go']['playlist']['Service']['DeletePlaylist'](arg1);
 }
@@ -26,6 +30,10 @@ export function EnsureDefaultPlaylist() {
   return window['go']['playlist']['Service']['EnsureDefaultPlaylist']();
 }
 
+export function EvaluateSmartPlaylist(arg1) {
+  return window['go']['playlist']['Service']['EvaluateSmartPlaylist'](arg1);
+}
+
 export function FindDuplicateTracksInPlaylist(arg1, arg2) {
   return window['go']['playlist']['Service']['FindDuplicateTracksInPlaylist'](arg1, arg2);
 }
@@ -109,3 +117,15 @@ export function SetFavoritesConfig(arg1) {
 export function ToggleDefaultPlaylistTrack(arg1) {
   return window['go']['playlist']['Service']['ToggleDefaultPlaylistTrack'](arg1);
 }
+
+export function UpdateSmartPlaylistRules(arg1, arg2) {
+  return window['go']['playlist']['Service']['UpdateSmartPlaylistRules'](arg1, arg2);
+}
+
+export function GetSmartPlaylistRules(arg1) {
+  return window['go']['playlist']['Service']['GetSmartPlaylistRules'](arg1);
+}
+
+export function PreviewSmartPlaylist(arg1) {
+  return window['go']['playlist']['Service']['PreviewSmartPlaylist'](arg1);
+}