feat(14-01): add PGlite test helper and generate initial PostgreSQL migration

- Rewrite tests/helpers/db.ts to use drizzle-orm/pglite with async createTestDb()
- Generate initial migration with 13 CREATE TABLE statements in drizzle-pg/
- Add drizzle-pg to biome ignore list (generated files)
- PGlite smoke test confirms migrations apply and seed works

drizzle-pg/meta/_journal.json

@@ -0,0 +1,13 @@
+{
+  "version": "7",
+  "dialect": "postgresql",
+  "entries": [
+    {
+      "idx": 0,
+      "version": "7",
+      "when": 1775297839520,
+      "tag": "0000_fuzzy_shiva",
+      "breakpoints": true
+    }
+  ]
+}