chore: add package.json, tsconfig pair, and vitest config

ESM-only, Node 20+, ships pre-compiled dist/. Peer dependency on
better-sqlite3 >=11 <13. Dev pins: typescript ^5.5, vitest ^4.0
(resolved to 4.1.6), better-sqlite3 12.6.2 (matches authd).

tsconfig.json (noEmit) is the dev/test config; tsconfig.build.json
extends it and emits .js + .d.ts to dist/. Relative imports inside src/
use .js extensions so the emitted JS resolves correctly at runtime.

tsconfig.json

@@ -0,0 +1,16 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ES2022",
+    "moduleResolution": "bundler",
+    "lib": ["ES2022"],
+    "strict": true,
+    "esModuleInterop": true,
+    "allowImportingTsExtensions": true,
+    "noEmit": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true
+  },
+  "include": ["src/**/*", "tests/**/*"]
+}