Add customizable home dashboard with per-user pinned apps

- Users can pin/unpin any available service on their home page via a
  Customize mode; preferences persisted via PATCH /api/users/me/preferences
- Time-aware greeting renders the user's display name through React JSX
  (HTML-escaped by design — no dangerouslySetInnerHTML used)
- Added dashboard_app_ids JSON column to users table (migration c7e8f9a0b1d2)
- /settings now routes to a placeholder page

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

backend/app/models/user.py

@@ -1,7 +1,7 @@
 import uuid
 from typing import TYPE_CHECKING
 
-from sqlalchemy import Boolean, String
+from sqlalchemy import Boolean, JSON, String
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.database import Base
@@ -21,6 +21,8 @@ class User(Base):
     # Role flag — True = admin, False = regular user.
     # Never exposed in API responses; set only by direct DB or admin tooling.
     is_superuser: Mapped[bool] = mapped_column(Boolean, default=False)
+    # List of service IDs pinned to the user's home dashboard.
+    dashboard_app_ids: Mapped[list] = mapped_column(JSON, nullable=False, default=list)
 
     profile: Mapped["Profile"] = relationship(
         "Profile", back_populates="user", uselist=False, cascade="all, delete-orphan"