Exclude test files from tsc build to fix CI

The build step runs `tsc && vite build`, and the test files that import
Node.js built-ins (fs, path) and use __dirname were causing TS2307 and
TS2304 errors during compilation. Excluding test files from tsconfig
keeps the build clean while vitest handles its own TypeScript resolution.

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

app/tsconfig.json

@@ -17,5 +17,6 @@
     "noFallthroughCasesInSwitch": true,
     "forceConsistentCasingInFileNames": true
   },
-  "include": ["src"]
+  "include": ["src"],
+  "exclude": ["src/**/*.test.ts", "src/**/*.test.tsx", "src/test"]
 }