Migrate from JSON to PostgreSQL, update SLA to 99.5%

- Replace JSON file storage with PostgreSQL (pg package)
- Add db.ts service for connection pool and schema init
- Rewrite keys.ts, verification.ts, usage.ts for async PostgreSQL
- Update all routes for async function signatures
- Add migration script (scripts/migrate-to-postgres.mjs)
- Update docker-compose.yml with DATABASE_* env vars
- Change SLA from 99.9% to 99.5% in landing page

src/services/db.ts

@@ -0,0 +1,65 @@
+import pg from "pg";
+
+const { Pool } = pg;
+
+const pool = new Pool({
+  host: process.env.DATABASE_HOST || "172.17.0.1",
+  port: parseInt(process.env.DATABASE_PORT || "5432", 10),
+  database: process.env.DATABASE_NAME || "docfast",
+  user: process.env.DATABASE_USER || "docfast",
+  password: process.env.DATABASE_PASSWORD || "docfast",
+  max: 10,
+  idleTimeoutMillis: 30000,
+});
+
+pool.on("error", (err) => {
+  console.error("Unexpected PostgreSQL pool error:", err);
+});
+
+export async function initDatabase(): Promise<void> {
+  const client = await pool.connect();
+  try {
+    await client.query(`
+      CREATE TABLE IF NOT EXISTS api_keys (
+        key TEXT PRIMARY KEY,
+        tier TEXT NOT NULL DEFAULT 'free',
+        email TEXT NOT NULL DEFAULT '',
+        created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+        stripe_customer_id TEXT
+      );
+      CREATE INDEX IF NOT EXISTS idx_api_keys_email ON api_keys(email);
+      CREATE INDEX IF NOT EXISTS idx_api_keys_stripe ON api_keys(stripe_customer_id);
+
+      CREATE TABLE IF NOT EXISTS verifications (
+        id SERIAL PRIMARY KEY,
+        email TEXT NOT NULL,
+        token TEXT NOT NULL UNIQUE,
+        api_key TEXT NOT NULL,
+        created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+        verified_at TIMESTAMPTZ
+      );
+      CREATE INDEX IF NOT EXISTS idx_verifications_email ON verifications(email);
+      CREATE INDEX IF NOT EXISTS idx_verifications_token ON verifications(token);
+
+      CREATE TABLE IF NOT EXISTS pending_verifications (
+        email TEXT PRIMARY KEY,
+        code TEXT NOT NULL,
+        created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+        expires_at TIMESTAMPTZ NOT NULL,
+        attempts INT NOT NULL DEFAULT 0
+      );
+
+      CREATE TABLE IF NOT EXISTS usage (
+        key TEXT PRIMARY KEY,
+        count INT NOT NULL DEFAULT 0,
+        month_key TEXT NOT NULL
+      );
+    `);
+    console.log("PostgreSQL tables initialized");
+  } finally {
+    client.release();
+  }
+}
+
+export { pool };
+export default pool;