feat(usage): real-time stats refresh + fix codex sync panic on non-ASCII model names (#3027)

The usage dashboard previously only refreshed on app restart for users
who don't route through the cc-switch proxy. Two issues were involved:

1. The session-sync background task panicked when a Codex model name
   contained non-ASCII characters (e.g. `【官】glm-5.1`), because
   `normalize_codex_model` sliced `&name[name.len() - 11..]` without
   verifying char boundaries. Once the task panicked, no session logs
   were imported until the app was restarted (where startup-time
   `rollup_and_prune` happened to flush pending data).

2. Even with sync working, the dashboard only polled every 30s and
   skipped polling when the window was unfocused, so freshly-imported
   data was invisible until the next poll or window refocus.

Fixes
-----

* `normalize_codex_model`: guard the 11-byte ISO-date suffix slice with
  `is_char_boundary` + `is_ascii` checks. ASCII-only suffix means the
  date-stripping logic is correct, and non-ASCII names (which can never
  be valid date suffixes anyway) now bypass the slice safely.

* New `usage_events` module that emits `usage-log-recorded` to the
  frontend whenever `proxy_request_logs` actually gains a new row.
  Sources covered: proxy `log_request`, Claude/Codex/Gemini session
  sync, and startup `rollup_and_prune`. Notifications use a global
  `OnceLock<AppHandle>` so call sites that don't already hold an
  `AppHandle` (e.g. `UsageLogger`) can notify without signature churn.

* 200ms debounce in `notify_log_recorded` collapses bursts (a single
  Codex sync importing 3000+ entries triggers ~2 emits, not 3000) so
  the frontend's `invalidateQueries` is never spammed.

* Frontend `useUsageEventBridge` listens for the event and invalidates
  `usageKeys.all`. Hook is mounted only on `UsageDashboard`, so the
  listener is unsubscribed automatically when the user navigates away.

Verification
------------

* `cargo check` passes (existing 25 dead-code warnings in
  `commands/misc.rs` are pre-existing and unrelated).
* `tsc --noEmit` passes.
* Manually verified end-to-end: a Codex sync run that imported 3145
  entries produced 2 debounced emits, both logged as `emit
  usage-log-recorded 成功`, and the dashboard updated within ~200ms.

Behaviour notes
---------------

* `INSERT OR IGNORE` paths (Claude/Codex session sync) only notify when
  the row is actually inserted, so dedup-skipped writes don't trigger
  empty refreshes.
* Gemini's `INSERT … ON CONFLICT … DO UPDATE` path reuses the existing
  `conn.changes() > 0` check and only notifies when token counts truly
  changed.
* `rollup_and_prune` notifies once per pruning cycle (at most once per
  app start) so the dashboard reflects the new aggregate state.

Co-authored-by: in30mn1a <in30mn1a@users.noreply.github.com>

src-tauri/src/proxy/usage/logger.rs

@@ -102,6 +102,9 @@ impl<'a> UsageLogger<'a> {
         )
         .map_err(|e| AppError::Database(format!("记录请求日志失败: {e}")))?;
 
+        // 通知前端使用统计有更新（200ms 防抖合并，不阻塞写入路径）
+        crate::usage_events::notify_log_recorded();
+
         Ok(())
     }