feat(14-01): rewrite database foundation from SQLite to PostgreSQL

- Replace all 13 sqliteTable definitions with pgTable (pg-core)
- Convert integer timestamps to native timestamp type with defaultNow()
- Convert real columns to doublePrecision, integer used to boolean
- Rewrite db connection to use postgres.js driver with DATABASE_URL
- Rewrite migrate.ts to use postgres-js migrator targeting drizzle-pg/
- Convert seed.ts to async
- Update drizzle.config.ts to postgresql dialect
- Install postgres and @electric-sql/pglite, remove better-sqlite3

drizzle.config.ts

@@ -1,10 +1,12 @@
 import { defineConfig } from "drizzle-kit";
 
 export default defineConfig({
-	out: "./drizzle",
+	out: "./drizzle-pg",
 	schema: "./src/db/schema.ts",
-	dialect: "sqlite",
+	dialect: "postgresql",
 	dbCredentials: {
-		url: process.env.DATABASE_PATH || "gearbox.db",
+		url:
+			process.env.DATABASE_URL ||
+			"postgresql://gearbox:gearbox@localhost:5432/gearbox",
 	},
 });