fix(build): remove sharp devDep — breaks Docker --ignore-scripts install

sharp uses postinstall to download native binaries. Docker build uses
pnpm install --ignore-scripts which skips this → build fails on server.
PNG icons already generated and committed, sharp no longer needed.

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

package.json

@@ -42,7 +42,6 @@
     "@types/react-dom": "^19",
     "eslint": "^9",
     "eslint-config-next": "16.2.9",
-    "sharp": "^0.35.1",
     "tailwindcss": "^4",
     "typescript": "^5"
   }