Fix TypeScript config for .ts import extensions

- allowImportingTsExtensions: true + noEmit: true in tsconfig
- build script runs tsc --noEmit (type-check only)
- Dockerfile simplified to single stage using tsx at runtime
  (no tsc compilation needed; tsx handles .ts imports natively)

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

tsconfig.json

@@ -1,18 +1,15 @@
 {
   "compilerOptions": {
     "target": "ES2022",
-    "module": "ESNext",
-    "moduleResolution": "Bundler",
-    "outDir": "dist",
-    "rootDir": "src",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "allowImportingTsExtensions": true,
+    "noEmit": true,
     "strict": true,
     "esModuleInterop": true,
     "skipLibCheck": true,
     "forceConsistentCasingInFileNames": true,
-    "resolveJsonModule": true,
-    "declaration": true,
-    "declarationMap": true,
-    "sourceMap": true
+    "resolveJsonModule": true
   },
   "include": ["src/**/*"],
   "exclude": ["node_modules", "dist", "tests"]