feat: add UpdatePlan and history types to frontend API

Add TypeScript interfaces and API methods for new update system:

**New Types:**
- UpdatePlan: Deployment-specific update plan with canAutoUpdate flag
- UpdateHistoryEntry: Complete audit log entry with all metadata

**New API Methods:**
- getUpdatePlan(version, channel?) - Get deployment-specific update plan
- getUpdateHistory(limit?, status?) - List update history with filters
- getUpdateHistoryEntry(eventId) - Get specific history entry details

These types match the backend Go structs and enable frontend
integration with the adapter-based update system.

Next: Implement UI components (confirmation modal, progress modal,
update banner enhancements, settings history panel).

frontend-modern/src/api/updates.ts

@@ -29,6 +29,40 @@ export interface VersionInfo {
   deploymentType?: string;
 }
 
+export interface UpdatePlan {
+  canAutoUpdate: boolean;
+  instructions?: string[];
+  prerequisites?: string[];
+  estimatedTime?: string;
+  requiresRoot: boolean;
+  rollbackSupport: boolean;
+  downloadUrl?: string;
+}
+
+export interface UpdateHistoryEntry {
+  event_id: string;
+  timestamp: string;
+  action: 'update' | 'rollback';
+  channel: string;
+  version_from: string;
+  version_to: string;
+  deployment_type: string;
+  initiated_by: 'user' | 'auto' | 'api';
+  initiated_via: 'ui' | 'cli' | 'script' | 'webhook';
+  status: 'in_progress' | 'success' | 'failed' | 'rolled_back' | 'cancelled';
+  duration_ms: number;
+  backup_path?: string;
+  log_path?: string;
+  error?: {
+    message: string;
+    code?: string;
+    details?: string;
+  };
+  download_bytes?: number;
+  related_event_id?: string;
+  notes?: string;
+}
+
 export class UpdatesAPI {
   static async checkForUpdates(channel?: string): Promise<UpdateInfo> {
     const url = channel ? `/api/updates/check?channel=${channel}` : '/api/updates/check';
@@ -49,4 +83,26 @@ export class UpdatesAPI {
   static async getVersion(): Promise<VersionInfo> {
     return apiFetchJSON('/api/version');
   }
+
+  static async getUpdatePlan(version: string, channel?: string): Promise<UpdatePlan> {
+    const url = channel
+      ? `/api/updates/plan?version=${version}&channel=${channel}`
+      : `/api/updates/plan?version=${version}`;
+    return apiFetchJSON(url);
+  }
+
+  static async getUpdateHistory(
+    limit?: number,
+    status?: string
+  ): Promise<UpdateHistoryEntry[]> {
+    const params = new URLSearchParams();
+    if (limit) params.append('limit', limit.toString());
+    if (status) params.append('status', status);
+    const url = `/api/updates/history${params.toString() ? `?${params.toString()}` : ''}`;
+    return apiFetchJSON(url);
+  }
+
+  static async getUpdateHistoryEntry(eventId: string): Promise<UpdateHistoryEntry> {
+    return apiFetchJSON(`/api/updates/history/entry?id=${eventId}`);
+  }
 }