Add quak helper list-missing-thumbnails and fix-missing-thumbnails

list-missing-thumbnails: iterates all files across all collections,
fetches each thumbnail from the CDN, reports any that are missing or
empty. Deduplicates by file ID across collections.

fix-missing-thumbnails: for each missing thumbnail, downloads the
original file, generates a 720px JPEG thumbnail via sharp, encrypts
it with secretstream push (encryptBlob), uploads to a presigned URL,
and registers the new thumbnail via PUT /files/thumbnail.

New crypto: encryptBlob (secretstream push, single chunk TAG_FINAL).
New ApiClient methods: getUploadURL, putFile, putJSON, updateThumbnail.
New Client method: getApiClient() for modules that need raw API access.

Deps: sharp 0.34.5 (image processing), @types/sharp 0.32.0.

package.json

@@ -31,6 +31,7 @@
         "@eslint/js": "9.38.0",
         "@types/libsodium-wrappers-sumo": "0.8.2",
         "@types/node": "22.18.13",
+        "@types/sharp": "0.32.0",
         "eslint": "9.38.0",
         "prettier": "3.8.1",
         "typescript": "5.9.3",
@@ -41,6 +42,7 @@
         "commander": "14.0.3",
         "env-paths": "4.0.0",
         "fast-srp-hap": "2.0.4",
-        "libsodium-wrappers-sumo": "0.8.4"
+        "libsodium-wrappers-sumo": "0.8.4",
+        "sharp": "0.34.5"
     }
 }