feat: Implement content-based offer IDs with SHA-256 hashing

- Added hash-id.ts utility for SHA-256 content hashing
- Offer IDs now generated from hash of {sdp, topics} (sorted)
- Removed peerId from hash (inferred from authentication)
- Server generates deterministic IDs for idempotent offer creation
- Updated SQLite and D1 storage implementations
- Removed optional id field from CreateOfferRequest
- Same offer content always produces same ID

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tsconfig.json

@@ -0,0 +1,20 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "ESNext",
+    "lib": ["ES2020"],
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "noEmit": true,
+    "types": ["@types/node", "@cloudflare/workers-types"]
+  },
+  "include": ["src/**/*.ts"],
+  "exclude": ["node_modules", "dist"]
+}