refactor: auto-init guest chat quota on first read, clean up logs

- Remove unused `quotaWarningThreshold` and `warningThreshold` getter from `GuestChatQuota` DTO
- Apply get-or-init pattern in `ChatStorage.getGuestDailyChatQuota` and `getGuestTotalQuota`: when no existing value, initialize with DTO defaults (`threshold` = max per day, `totalQuotaDefault`) and return the seeded data
- Fall back to original `null` result if initialization write fails
- Consolidate logging strategy: drop per-actor trace logs in `chat-machine.ts`, keep business-decision logs in 3 assign actions, move all actor ENTRY/API/DONE chains to `chat-machine.actors.ts` and helper load logs to `chat-machine.helpers.ts`

src/stores/chat/chat-state.ts

@@ -29,8 +29,6 @@ export interface ChatState {
    */
   wsConnected: boolean;
   /** 游客剩余配额（次/天）—— **仅**游客业务展示用
-   * - default 0 = "未初始化" / "已耗尽"（同码，靠 `isGuest` 区分）
-   * - 非游客：永不被赋值（业务事实"无消息限制"）
    */
   guestRemainingQuota: number;
   /** 游客总配额（仅游客展示用） */