fix(permissions): fix 10 high-priority permission system issues

P8: Invalidate all Redis sessions when is_system_admin changes
- Added is_system_admin to UserUpdate schema and UserResponse
- Added invalidate_all_user_sessions call in users.py route
- Added is_system_admin param to user_service.update_user

P9: Remove no-op permission resolution strategies
- Only highest_wins supported, others removed as no-ops
- Updated tenant.py CheckConstraint to only allow highest_wins
- Added KI-Kommentar in permissions.py

P10: Remove legacy check_permission from auth.py
- Removed duplicate check_permission and filter_fields_by_permission
- Fixed ai_copilot_service.py to use permissions.check_permission
- Updated ai_copilot route to pass resolved permissions dict

P11: Verified — no guest_users remnants found

P12: Migrate ContactFolderPermission to EntityPermission
- contact_folder_permission_service now delegates to entity_permission_service
- contact_folder_service uses EntityPermission queries
- Removed ContactFolderPermission from models/__init__.py
- Created migration 0114 to migrate data and drop table

P13: Added RLS migration history comment in alembic/env.py

P14: Verified — services already apply visibility_filter
- saved_filters/views filter by user_id (personal data)
- workspaces are UI context only
- notifications already filter by entity access

P15: Split entity_permission_service.py (932 lines) into 4 modules
- permission_resolver.py: get_effective_access, get_visible_ids, etc.
- permission_cache.py: Redis caching functions
- permission_audit.py: Audit logging helpers
- entity_permission_service.py: CRUD operations + re-exports

P16: Centralize PERM_RANK in permissions.py
- Single source: app.core.permissions.PERM_RANK
- Updated all services to import from permissions.py

P17: Fix MIGRATION_DATABASE_URL to use crm_migration
- docker-compose.yaml defaults changed from crm_user to crm_migration
- .env.docker.example updated
- prestart.sh comment updated

app/schemas/user.py

@@ -45,6 +45,7 @@ class UserUpdate(BaseModel):
     role: str | None = None
     role_id: str | None = Field(default=None, description="UUID of a custom Role; send null to clear")
     is_active: bool | None = None
+    is_system_admin: bool | None = Field(None, description="System admin flag — requires system admin to set")
     current_password: str | None = Field(None, description="Required when changing password")
     new_password: str | None = Field(None, min_length=8, description="New password")
 
@@ -59,6 +60,7 @@ class UserResponse(BaseModel):
     role: str
     role_id: str | None = None
     is_active: bool
+    is_system_admin: bool = False
     tenant_id: str