feat: add mergerfs mover and snapraid integration

New 'Almacenamiento' page with:
- Auto-detection of rsync, mergerfs, snapraid binaries and mergerfs mount
- Configurable pool settings (source/dest, macOS cleanup, rsync flags)
- Mergerfs mover with dry-run preview and live SSE output streaming
- SnapRAID diff/sync/scrub/check with live SSE output
- Async job system (1 concurrent job) with SSE streaming
- Job history table

Backend:
- internal/storage/ package with capabilities, mergerfs, snapraid, jobs
- storage_config and storage_jobs DB tables (migration 0008)
- GET/PUT /api/storage/config, GET /api/storage/capabilities
- POST/GET /api/storage/jobs, GET /api/storage/jobs/{id}/stream
- Storage operations disabled when NASCTL_EXEC_SYSTEM=false

Closes #new-feature

web/src/App.tsx

@@ -11,6 +11,7 @@ import Nfs from "./pages/Nfs";
 import Log from "./pages/Log";
 import Settings from "./pages/Settings";
 import Files from "./pages/Files";
+import Storage from "./pages/Storage";
 
 type AuthState = { loading: boolean; authenticated: boolean; username: string };
 
@@ -56,6 +57,7 @@ export default function App() {
           <Route path="/files" element={<Files />} />
           <Route path="/samba" element={<Samba />} />
           <Route path="/nfs" element={<Nfs />} />
+          <Route path="/storage" element={<Storage />} />
           <Route path="/log" element={<Log />} />
           <Route path="/settings" element={<Settings />} />
           <Route path="*" element={<Navigate to="/" replace />} />