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/stores/chat.ts

@@ -37,6 +37,8 @@ export interface Session {
   model?: string
   provider?: string
   messageCount?: number
+  inputTokens?: number
+  outputTokens?: number
 }
 
 function uid(): string {
@@ -147,6 +149,8 @@ function mapHermesSession(s: SessionSummary): Session {
     model: s.model,
     provider: (s as any).billing_provider || '',
     messageCount: s.message_count,
+    inputTokens: s.input_tokens,
+    outputTokens: s.output_tokens,
   }
 }
 
@@ -203,6 +207,8 @@ export const useChatStore = defineStore('chat', () => {
         if (detail && detail.messages) {
           const mapped = mapHermesMessages(detail.messages)
           activeSession.value.messages = mapped
+          activeSession.value.inputTokens = detail.input_tokens
+          activeSession.value.outputTokens = detail.output_tokens
           // Update title: use Hermes title, or fallback to first user message
           if (detail.title) {
             activeSession.value.title = detail.title