Set up npm workspaces monorepo with Turborepo and local infra

Postgres and Redis run via docker compose on non-default ports (5447/6380)
to avoid clashing with other local services. React is pinned to a single
version across workspaces because Expo requires it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MzFywujuH9TiuXbr9vjoX8

tsconfig.base.json

@@ -0,0 +1,16 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "lib": ["ES2023"],
+    "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "forceConsistentCasingInFileNames": true,
+    "noEmit": true
+  }
+}