feat(ui): add a logger to change log level and permit better diagnostics

in this case logs are added in the delta upload worker

you can increase verbosity from console via:

```javascript
// Usage:
oxi.setLogLevel('oxi:upload', 'debug')    // deep dive
oxi.setLogLevel('oxi:upload', 'warn')     // quiet
oxi.log.setLevel('debug')                  // everything to debug
```

values are stored in localstorage

example:

```
oxi.setLogLevel('oxi:upload', 'debug');
'oxi:upload → debug'
deltaUpload.ts:120 [f32ce1] delta start {file: 'Revue de presseg.odp', size: 23658927}
deltaUpload.ts:185 [f32ce1] worker: worker start {file: 'Revue de presseg.odp', size: 23658927}
deltaUpload.ts:186 [f32ce1] worker: wasm loaded
deltaUpload.ts:186 [f32ce1] worker: hashed — blake3=150edbc35f3475a0bdeecd15fe5278dda305ce3b27e53e9c40515a69f0b883f3 (76 chunks)
deltaUpload.ts:186 [f32ce1] worker: negotiate: 76 hashes → 76 missing, 0 dedup'd
deltaUpload.ts:186 [f32ce1] worker: chunk PUT: 28 chunks, 8825338 bytes
deltaUpload.ts:186 [f32ce1] worker: chunk PUT: 29 chunks, 8950230 bytes
deltaUpload.ts:186 [f32ce1] worker: chunk PUT: 19 chunks, 5883663 bytes
deltaUpload.ts:186 [f32ce1] worker: ✅ committed — uploaded 23 658 927 B (no dedup, blake3=150edbc35f3475a0bdeecd15fe5278dda305ce3b27e53e9c40515a69f0b883f3)
deltaUpload.ts:185 [f32ce1] worker: commit HTTP 201 {blake3: '150edbc35f3475a0bdeecd15fe5278dda305ce3b27e53e9c40515a69f0b883f3', uploadedBytes: 23658927, reusedBytes: 0, totalBytes: 23658927, attempt: 0}
deltaUpload.ts:213 [f32ce1] delta done {file: 'Revue de presseg.odp', blake3: '150edbc35f3475a0bdeecd15fe5278dda305ce3b27e53e9c40515a69f0b883f3', savedBytes: 0, uploadedBytes: 23658927}
```

frontend/package.json

@@ -47,6 +47,7 @@
     "vitest": "^4.1.9"
   },
   "dependencies": {
-    "@serenity-kit/opaque": "^1.1.0"
+    "@serenity-kit/opaque": "^1.1.0",
+    "loglevel": "^1.9.2"
   }
 }