fix(05-04): pre-select document client and add manual email entry

- PreparePanel now receives separate assignedClientId (nullable) and
  defaultClientId props so it can distinguish an explicitly locked
  client from just a default
- When document already has assignedClientId: show locked read-only
  display; user cannot change the primary recipient
- When document has no assignedClientId: default to document owner in
  dropdown but allow changing; option to clear and enter email manually
- Added textarea for additional/CC email addresses (comma or newline
  separated) that is always visible for either mode
- POST /api/documents/[id]/prepare now accepts and stores emailAddresses
  array alongside assignedClientId
- Added email_addresses jsonb column to documents table via migration
  0004_military_maximus.sql

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

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

@@ -29,6 +29,13 @@
       "when": 1773985969484,
       "tag": "0003_cool_natasha_romanoff",
       "breakpoints": true
+    },
+    {
+      "idx": 4,
+      "version": "7",
+      "when": 1773987640772,
+      "tag": "0004_military_maximus",
+      "breakpoints": true
     }
   ]
 }