fix(6229): remove the Profile settings page — nothing read it

The Profile tab said an assistant used it to personalise chat and a daily
journal. Neither exists, and nothing read the profile: the page saved to
user_profiles and the backup carried it. Removed the tab, the client calls,
/api/profile, the service and the model, and migration 0123 drops the table
(downgrade recreates it empty).

Backup format v27 stops writing user_profiles; an older archive carrying the
section still restores, and the file-restore integration test now proves it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/api/client.ts

@@ -500,24 +500,6 @@ export const createApiKey = (name: string, scope: 'read' | 'write') =>
 
 export const revokeApiKey = (id: number) => apiDelete(`/api/api-keys/${id}`)
 
-// ── User Profile ─────────────────────────────────────────────────────────────
-
-export interface UserProfile {
-  display_name: string
-  job_title: string
-  industry: string
-  expertise_level: 'novice' | 'intermediate' | 'expert'
-  response_style: 'concise' | 'balanced' | 'detailed'
-  tone: 'casual' | 'professional' | 'technical'
-  interests: string[]
-  work_schedule: { days?: string[]; start?: string; end?: string }
-}
-
-export const getProfile = () => apiGet<UserProfile>('/api/profile')
-export const updateProfile = (data: Partial<UserProfile>) =>
-  apiPut<UserProfile>('/api/profile', data)
-
-
 // ── Note Versions (pinning) ──────────────────────────────────────────────────
 
 import type { NoteVersion } from '../types/task'