init: FileDrop phase1 architecture and scaffold

- Rust axum signaling server with WebSocket support
- Lit + TypeScript frontend with Vite
- Redis session storage with TTL
- WebRTC transport and crypto client stubs
- Phase1 architecture plan in plans/
- Deploy directory structure prepared

web/tsconfig.json

@@ -0,0 +1,15 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "declaration": true
+  },
+  "include": ["src"]
+}