feat(ios): implement getContentCache and clearContentCache methods

Implemented content cache management methods matching Android functionality:

getContentCache():
- Retrieves latest cached content from Core Data
- Returns id, fetchedAt, ttlSeconds, payload, and meta
- Returns empty object if no cache exists
- Uses async Task for Core Data access

clearContentCache():
- Deletes all content cache entries from Core Data
- Uses NSBatchDeleteRequest for efficient deletion
- Saves context after deletion

iOS Adaptations:
- Uses Core Data (ContentCache entity) instead of SQLite
- Async/await pattern for Core Data operations
- JSON deserialization for payload
- Timestamp conversion (Date to milliseconds)

Progress: 21/52 methods implemented (40% complete)

ios/Plugin/DailyNotificationPlugin.swift

@@ -839,6 +839,89 @@ public class DailyNotificationPlugin: CAPPlugin {
         call.resolve()
     }
     
+    // MARK: - Content Management Methods
+    
+    /**
+     * Get content cache
+     * 
+     * Returns the latest cached content from Core Data.
+     * 
+     * Equivalent to Android's getContentCache method.
+     */
+    @objc func getContentCache(_ call: CAPPluginCall) {
+        print("DNP-PLUGIN: Getting content cache")
+        
+        Task {
+            do {
+                let context = persistenceController.container.viewContext
+                let request: NSFetchRequest<ContentCache> = ContentCache.fetchRequest()
+                request.sortDescriptors = [NSSortDescriptor(keyPath: \ContentCache.fetchedAt, ascending: false)]
+                request.fetchLimit = 1
+                
+                let results = try context.fetch(request)
+                
+                if let latest = results.first {
+                    let payload = try JSONSerialization.jsonObject(with: latest.payload!) as? [String: Any] ?? [:]
+                    
+                    let result: [String: Any] = [
+                        "id": latest.id ?? "",
+                        "fetchedAt": Int64((latest.fetchedAt?.timeIntervalSince1970 ?? 0) * 1000),
+                        "ttlSeconds": latest.ttlSeconds,
+                        "payload": payload,
+                        "meta": latest.meta ?? ""
+                    ]
+                    
+                    DispatchQueue.main.async {
+                        call.resolve(result)
+                    }
+                } else {
+                    // Return empty result if no cache
+                    DispatchQueue.main.async {
+                        call.resolve([:])
+                    }
+                }
+            } catch {
+                print("DNP-PLUGIN: Failed to get content cache: \(error)")
+                DispatchQueue.main.async {
+                    call.reject("Content cache retrieval failed: \(error.localizedDescription)")
+                }
+            }
+        }
+    }
+    
+    /**
+     * Clear content cache
+     * 
+     * Clears all content cache entries from Core Data.
+     * 
+     * Equivalent to Android's clearContentCache method.
+     */
+    @objc func clearContentCache(_ call: CAPPluginCall) {
+        print("DNP-PLUGIN: Clearing content cache")
+        
+        Task {
+            do {
+                let context = persistenceController.container.viewContext
+                let request: NSFetchRequest<NSFetchRequestResult> = ContentCache.fetchRequest()
+                let deleteRequest = NSBatchDeleteRequest(fetchRequest: request)
+                
+                try context.execute(deleteRequest)
+                try context.save()
+                
+                print("DNP-PLUGIN: Content cache cleared successfully")
+                
+                DispatchQueue.main.async {
+                    call.resolve()
+                }
+            } catch {
+                print("DNP-PLUGIN: Failed to clear content cache: \(error)")
+                DispatchQueue.main.async {
+                    call.reject("Failed to clear content cache: \(error.localizedDescription)")
+                }
+            }
+        }
+    }
+    
     // MARK: - Private Implementation Methods
     
     private func setupBackgroundTasks() {