feat: add account management, email verification, AI fixes, and user guides

- Profile settings, account transfer, delete/leave account flows
- Email verification with JWT tokens and Resend integration
- AI assistant/copilot fixes: markdown rendering, shared RAG helpers,
  token tracking, input refocus, model_validate usage
- User guides hub + detail pages with 13 topic guides
- Sidebar and top bar navigation for guides

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

backend/app/schemas/user.py

@@ -30,6 +30,10 @@ class UserCreate(UserBase):
 class UserUpdate(BaseModel):
     name: Optional[str] = Field(None, min_length=1, max_length=255)
     email: Optional[EmailStr] = None
+    current_password: Optional[str] = Field(None, description="Required when changing email")
+    phone: Optional[str] = Field(None, max_length=50)
+    job_title: Optional[str] = Field(None, max_length=255)
+    timezone: Optional[str] = Field(None, max_length=100)
 
 
 class UserLogin(BaseModel):
@@ -48,6 +52,11 @@ class UserResponse(UserBase):
     created_at: datetime
     last_login: Optional[datetime] = None
     deleted_at: Optional[datetime] = None
+    phone: Optional[str] = None
+    job_title: Optional[str] = None
+    timezone: str = "UTC"
+    avatar_url: Optional[str] = None
+    email_verified_at: Optional[datetime] = None
 
     class Config:
         from_attributes = True