fix(notes): add company_notes.updated_at, drop createdAt substitution

company_notes was missing updated_at — every other notes table has it,
and notes.service.ts substituted created_at into the response shape so
callers wouldn't notice. Add the column (defaulted + backfilled to
created_at for existing rows), wire the update path to set it on
edit, and drop the substitution from the read + edit handlers.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/db/schema/companies.ts

@@ -123,6 +123,7 @@ export const companyNotes = pgTable(
     mentions: text('mentions').array(),
     isLocked: boolean('is_locked').notNull().default(false),
     createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+    updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
   },
   (table) => [index('idx_compn_company').on(table.companyId)],
 );