fix(db): point db:migrate at the live appliance DB by default

`db:migrate` (and drizzle-kit's config default) resolved DATABASE_URL to
`./parking.sqlite` relative to packages/db — a stray, half-empty leftover DB,
not the real store at apps/server/parking.sqlite. Running `pnpm --filter
@parking/db db:migrate` with no env therefore migrated the wrong file and
failed on its broken state, while the real DB went untouched.

Default DATABASE_URL to ../../apps/server/parking.sqlite in both the db:migrate
script and drizzle.config.ts (an explicit DATABASE_URL still overrides). The
stray packages/db/parking.sqlite was untracked + already gitignored (*.sqlite);
deleted it from disk. Now `pnpm --filter @parking/db db:migrate` targets the
appliance DB out of the box.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

packages/db/drizzle.config.ts

@@ -8,6 +8,9 @@ export default defineConfig({
   schema: "./src/schema.ts",
   out: "./drizzle",
   dbCredentials: {
-    url: process.env.DATABASE_URL ?? "./parking.sqlite",
+    // Default to the live appliance DB (apps/server), NOT a stray ./parking.sqlite in
+    // this package. The `db:migrate` script also sets DATABASE_URL to this. Override with
+    // DATABASE_URL to target another DB.
+    url: process.env.DATABASE_URL ?? "../../apps/server/parking.sqlite",
   },
 });