feat: complete Phase 1 - game library, lifecycle, realtime sync

- Seed 33 popular games across 5 platforms via admin API script
- Add GameDetailDialog with game info and quick-team button
- Update GamesLibrary with game card click to open detail dialog
- Update Home hot games to open detail dialog instead of navigating
- Rewrite invitation accept: frontend auto-joins team + updates status
- Add user status reset on team dissolution (endGame)
- Add start game / dissolve buttons to TeamSessionPanel lifecycle
- Integrate realtime subscriptions in GroupView and Layout
- Add notification store realtime invitation listener
- Add placeholder images for game covers and avatars
- Remove Go hooks, add JS hooks placeholder + Docker mount

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/public/default-avatar.png

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="64" height="64" viewBox="0 0 64 64">
+  <rect fill="#e8f5e9" width="64" height="64" rx="32"/>
+  <text x="32" y="40" text-anchor="middle" fill="#059669" font-size="28">👤</text>
+</svg>

frontend/public/game-placeholder.png

@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="200" height="260" viewBox="0 0 200 260">
+  <rect fill="#e8f5e9" width="200" height="260"/>
+  <text x="100" y="120" text-anchor="middle" fill="#059669" font-size="48">🎮</text>
+  <text x="100" y="155" text-anchor="middle" fill="#6b7280" font-size="14">暂无封面</text>
+</svg>