feat(05-01): extend documents schema with 4 new columns + migration 0003

- Added SignatureFieldData interface export to schema.ts
- Added signatureFields (jsonb), textFillData (jsonb), assignedClientId (text), preparedFilePath (text) nullable columns to documents table
- Added jsonb import to drizzle-orm/pg-core imports
- Generated and applied migration 0003_cool_natasha_romanoff.sql

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

teressa-copeland-homes/drizzle/meta/_journal.json

@@ -22,6 +22,13 @@
       "when": 1773977523128,
       "tag": "0002_wealthy_zzzax",
       "breakpoints": true
+    },
+    {
+      "idx": 3,
+      "version": "7",
+      "when": 1773985969484,
+      "tag": "0003_cool_natasha_romanoff",
+      "breakpoints": true
     }
   ]
 }