feat: add usage statistics page, CLI improvements, and UI enhancements

- Add Usage Stats page with token breakdown, model distribution, and 30-day trend
- Pass through cache/cost token fields in BFF (cache_read/write_tokens, reasoning_tokens, actual_cost_usd)
- Add CLI commands: -v/--version, -h/--help, update/upgrade with auto-restart
- Auto-open browser on startup, auto-kill port conflicts (cross-platform)
- Validate all api_server config fields on startup (enabled, host, port, key, cors_origins)
- Add streaming thinking video animation with tool calls panel
- Add context token usage display (used / total) in chat header
- Sidebar: white logo area with shadow, dance video beside logo (canvas seamless loop)
- Fix sidebar nav scroll (app-main overflow-y: auto)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/i18n/locales/en.ts

@@ -30,6 +30,7 @@ export default {
     skills: 'Skills',
     memory: 'Memory',
     logs: 'Logs',
+    usage: 'Usage',
     channels: 'Channels',
     settings: 'Settings',
     connected: 'Connected',
@@ -43,6 +44,7 @@ export default {
     attachFiles: 'Attach files',
     stop: 'Stop',
     send: 'Send',
+    contextUsed: 'Context used:',
     sessions: 'Sessions',
     noSessions: 'No sessions',
     newChat: 'New Chat',
@@ -337,4 +339,25 @@ export default {
     zh: '中文',
     en: 'English',
   },
+
+  // Usage
+  usage: {
+    title: 'Usage Statistics',
+    refresh: 'Refresh',
+    totalTokens: 'Total Tokens',
+    inputTokens: 'Input',
+    outputTokens: 'Output',
+    totalSessions: 'Total Sessions',
+    avgPerDay: '~{n}/day avg',
+    estimatedCost: 'Est. Cost',
+    cacheHitRate: 'Cache Hit Rate',
+    modelBreakdown: 'Model Breakdown',
+    dailyTrend: 'Daily Usage (Last 30 Days)',
+    date: 'Date',
+    tokens: 'Tokens',
+    cache: 'Cache',
+    sessions: 'Sessions',
+    cost: 'Cost',
+    noData: 'No usage data',
+  },
 }