feat(11.1-01): DB migration, API routes, schema type updates for agent initials storage

- Add agentInitialsData text column to users table (drizzle/0009_luxuriant_catseye.sql)
- Add 'agent-initials' to SignatureFieldType union in schema.ts
- Update isClientVisibleField() to exclude both agent-signature and agent-initials
- Create GET/PUT /api/agent/initials route with auth guard and 50KB size limit

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

@@ -64,6 +64,13 @@
       "when": 1774123280818,
       "tag": "0008_windy_cloak",
       "breakpoints": true
+    },
+    {
+      "idx": 9,
+      "version": "7",
+      "when": 1774126681669,
+      "tag": "0009_luxuriant_catseye",
+      "breakpoints": true
     }
   ]
 }