Rename @reviq/utils to @reviq/server-utils and add package READMEs

- Rename packages/utils/ to packages/server-utils/
- Update all imports and package.json references
- Add READMEs for frontend-utils, server-utils, and common packages
- Update main README with new package structure

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/db/package.json

@@ -19,7 +19,7 @@
   "dependencies": {
     "@noble/hashes": "^2.0.1",
     "@reviq/db-schema": "workspace:*",
-    "@reviq/utils": "workspace:*",
+    "@reviq/server-utils": "workspace:*",
     "@scure/base": "^2.0.0",
     "kysely": "^0.28.9",
     "pg": "^8.13.1"