feat(db): add incremental upsert seed script for WordNet vocabulary

Implements packages/db/src/seed.ts — reads all JSON files from
scripts/datafiles/, validates filenames against supported language
codes and POS, and upserts synsets into  and
via onConflictDoNothing. Safe to re-run; produces 0 writes on
a duplicate run.

packages/db/drizzle/meta/_journal.json

@@ -1 +1,13 @@
-{"version":"7","dialect":"postgresql","entries":[]}
+{
+  "version": "7",
+  "dialect": "postgresql",
+  "entries": [
+    {
+      "idx": 0,
+      "version": "7",
+      "when": 1774721919883,
+      "tag": "0000_bitter_turbo",
+      "breakpoints": true
+    }
+  ]
+}