Feature: VdevTree rekursiv + Disk-Aktionen (Offline/Online/Detach/Clear)

- VdevTree rendert jetzt alle Ebenen (pool → mirror → sda/sdb)
- Disk-⋮-Menü: Clear Disk Errors, Offline, Online, Detach
- Backend: neue Endpoints /disk/offline, /disk/online, /disk/detach

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

frontend/lib/api.ts

@@ -233,6 +233,26 @@ export class ZFSManagerAPI {
     return response.data
   }
 
+  async diskOffline(poolName: string, disk: string): Promise<{ status: string }> {
+    const response = await this.client.post(`/api/pools/${poolName}/disk/offline`, null, { params: { disk } })
+    return response.data
+  }
+
+  async diskOnline(poolName: string, disk: string): Promise<{ status: string }> {
+    const response = await this.client.post(`/api/pools/${poolName}/disk/online`, null, { params: { disk } })
+    return response.data
+  }
+
+  async diskDetach(poolName: string, disk: string): Promise<{ status: string }> {
+    const response = await this.client.post(`/api/pools/${poolName}/disk/detach`, null, { params: { disk } })
+    return response.data
+  }
+
+  async clearDiskErrors(poolName: string, disk: string): Promise<{ status: string }> {
+    const response = await this.client.post(`/api/pools/${poolName}/clear`, null, { params: { disk } })
+    return response.data
+  }
+
   // Datasets
   async getDatasets(pool: string = "tank"): Promise<Dataset[]> {
     const response = await this.client.get("/api/datasets/", { params: { pool } })