feat: AI cost tracking, pre-launch balance check, low balance alerts

- store/ai_charge.go: local AI cost tracking per call (SQLite)
- wallet/usdc.go: shared USDC balance query (Base chain RPC)
- Pre-launch: estimate daily cost + runway days
- Low balance: warn <$1, error at $0 (every 10 cycles)
- API: GET /api/ai-costs for cost history
- Frontend: model cards show price per call
- Frontend: wallet create + QR deposit + balance display

api/server.go

@@ -89,6 +89,7 @@ func (s *Server) setupRoutes() {
 
 		// Wallet validation (no authentication required — used by frontend config form)
 		api.POST("/wallet/validate", s.handleWalletValidate)
+		api.POST("/wallet/generate", s.handleWalletGenerate)
 
 		// Crypto related endpoints (no authentication required, not exposed to bot)
 		api.GET("/crypto/config", s.cryptoHandler.HandleGetCryptoConfig)
@@ -173,6 +174,10 @@ Body: {"show_in_competition":<bool>}`,
 				`:id = trader_id from GET /api/my-traders.`,
 				s.handleGetGridRiskInfo)
 
+			// AI cost tracking
+			s.route(protected, "GET", "/ai-costs", "Get AI call costs for a trader (?trader_id=xxx&period=today)", s.handleGetAICosts)
+			s.route(protected, "GET", "/ai-costs/summary", "Get AI cost summary (?period=today)", s.handleGetAICostsSummary)
+
 			// AI model configuration
 			s.routeWithSchema(protected, "GET", "/models", "List AI model configs",
 				`Returns: [{"id":"<EXACT id — use this as ai_model_id when creating/updating a trader>","name":"<display name>","provider":"<short provider name — NOT a valid id>","enabled":<bool>}]