fix: circuit breaker persistent cache with safety fixes (#281)

* fix: persist circuit breaker cache to IndexedDB across page reloads

On page reload, all 28+ circuit breaker in-memory caches are lost,
triggering 20-30 simultaneous POST requests to Vercel edge functions.

Wire the existing persistent-cache.ts (IndexedDB + localStorage +
Tauri fallback) into CircuitBreaker so every breaker automatically:

- Hydrates from IndexedDB on first execute() call (~1-5ms read)
- Writes to IndexedDB fire-and-forget on every recordSuccess()
- Falls back to stale persistent data on network failure
- Auto-disables for breakers with cacheTtlMs=0 (live pricing)

Zero consumer code changes -- all 28+ breaker call sites untouched.
Reloads within the cache TTL (default 10min) serve instantly from
IndexedDB with zero network calls.

Also adds deletePersistentCache() to persistent-cache.ts for clean
cache invalidation via clearCache().

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: add Playwright e2e tests for circuit breaker persistent cache

7 tests covering: IndexedDB persistence on success, hydration on new
instance, TTL expiry forcing fresh fetch, 24h stale ceiling rejection,
clearCache cleanup, cacheTtlMs=0 auto-disable, and network failure
fallback to stale persistent data.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: desktop cache deletion + clearCache race condition

P1: deletePersistentCache sent empty string to write_cache_entry,
which fails Rust's serde_json::from_str (not valid JSON). Add
dedicated delete_cache_entry Tauri command that removes the key
from the in-memory HashMap and flushes to disk.

P2: clearCache() set persistentLoaded=false, allowing a concurrent
execute() to re-hydrate stale data from IndexedDB before the async
delete completed. Remove the reset — after explicit clear there is
no reason to re-hydrate from persistent storage.

* fix: default persistCache to false, fix falsy data guard

P1b: 6 breakers store Date objects (weather, aviation, ACLED,
military-flights, military-vessels, GDACS) which become strings
after JSON round-trip. Callers like MapPopup.getTimeUntil() call
date.getTime() on hydrated strings → TypeError. Change default
to false (opt-in) so persistence requires explicit confirmation
that the payload is JSON-safe.

P2: `if (!entry?.data) return` drops valid falsy payloads (0,
false, empty string). Use explicit null/undefined check instead.

* fix: address blocking review issues on circuit breaker persistence

- clearCache() nulls persistentLoadPromise to orphan in-flight hydration
- delete_cache_entry defers disk flush to exit handler (avoids 14MB sync write)
- hydratePersistentCache checks TTL before setting lastDataState to 'cached'
- deletePersistentCache resets cacheDbPromise on IDB error + logs warning
- hydration catch logs warning instead of silently swallowing
- deletePersistentCache respects isStorageQuotaExceeded() for localStorage

---------

Co-authored-by: Elias El Khoury <efk@anghami.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/main.rs

@@ -314,6 +314,20 @@ fn read_cache_entry(cache: tauri::State<'_, PersistentCache>, key: String) -> Re
     Ok(cache.get(&key))
 }
 
+#[tauri::command]
+fn delete_cache_entry(cache: tauri::State<'_, PersistentCache>, key: String) -> Result<(), String> {
+    {
+        let mut data = cache.data.lock().unwrap_or_else(|e| e.into_inner());
+        data.remove(&key);
+    }
+    {
+        let mut dirty = cache.dirty.lock().unwrap_or_else(|e| e.into_inner());
+        *dirty = true;
+    }
+    // Disk flush deferred to exit handler (cache.flush) — avoids blocking main thread
+    Ok(())
+}
+
 #[tauri::command]
 fn write_cache_entry(app: AppHandle, cache: tauri::State<'_, PersistentCache>, key: String, value: String) -> Result<(), String> {
     let parsed_value: Value = serde_json::from_str(&value)
@@ -967,6 +981,7 @@ fn main() {
             get_desktop_runtime_info,
             read_cache_entry,
             write_cache_entry,
+            delete_cache_entry,
             open_logs_folder,
             open_sidecar_log_file,
             open_settings_window_command,