fix: resolve all TypeScript errors via proper Express 5 typed route params

- Add StringParams = Record<string, string> to types.ts
- Use Request<StringParams> in all route handlers across 14 files
- Clean up earlier as-cast workarounds in places.ts and admin.ts
- tsconfig.json: keep original (removed bad 'types:node' addition)
- package.json: restore @types/express back to ^5.0.6

server/tsconfig.json

@@ -9,7 +9,6 @@
     "esModuleInterop": true,
     "skipLibCheck": true,
     "forceConsistentCasingInFileNames": true,
-    "types": ["node"],
     "resolveJsonModule": true,
     "declaration": false,
     "sourceMap": true,