Feature: Snapshot-Tab in Datasets mit Kontextmenü (Clone/Rename/Rollback/Destroy)

- Snapshots direkt im Datasets-Tab ladbar (lazy, per Pool)
- Tabelle: Name, Created, Used, Referenced, Clones
- Kontextmenü (⋮) mit Clone, Rename, Roll Back, Destroy Snapshot
- Backend: /api/snapshots/clone + /api/snapshots/rename Endpoints

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

frontend/lib/api.ts

@@ -267,6 +267,16 @@ export class ZFSManagerAPI {
     return response.data
   }
 
+  async cloneSnapshot(snapshot: string, target: string): Promise<{ status: string }> {
+    const response = await this.client.post("/api/snapshots/clone", { snapshot, target })
+    return response.data
+  }
+
+  async renameSnapshot(snapshot: string, new_name: string): Promise<{ status: string }> {
+    const response = await this.client.post("/api/snapshots/rename", { snapshot, new_name })
+    return response.data
+  }
+
   // Shares — Samba
   async getSambaShares(): Promise<SambaShare[]> {
     const response = await this.client.get("/api/shares/samba")