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.

scripts/datafiles/test.json

@@ -0,0 +1,36 @@
+[
+  {
+    "synset_id": "ili:i35545",
+    "pos": "noun",
+    "translations": { "en": ["entity"], "it": ["cosa", "entità"] }
+  },
+  {
+    "synset_id": "ili:i35547",
+    "pos": "noun",
+    "translations": {
+      "en": ["abstraction", "abstract entity"],
+      "it": ["astrazione"]
+    }
+  },
+  {
+    "synset_id": "ili:i35549",
+    "pos": "noun",
+    "translations": {
+      "en": ["object", "physical object"],
+      "it": ["oggetto", "cosa"]
+    }
+  },
+  {
+    "synset_id": "ili:i35550",
+    "pos": "noun",
+    "translations": { "en": ["whole", "unit"], "it": ["insieme", "tutto"] }
+  },
+  {
+    "synset_id": "ili:i35553",
+    "pos": "noun",
+    "translations": {
+      "en": ["organism", "being"],
+      "it": ["essere vivente", "organismo", "organismo vivente"]
+    }
+  }
+]