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/api/sessions.ts

@@ -11,8 +11,13 @@ export interface SessionSummary {
   tool_call_count: number
   input_tokens: number
   output_tokens: number
+  cache_read_tokens: number
+  cache_write_tokens: number
+  reasoning_tokens: number
   billing_provider: string | null
   estimated_cost_usd: number
+  actual_cost_usd: number | null
+  cost_status: string
 }
 
 export interface SessionDetail extends SessionSummary {