POL-127: Add organizations table and championship ownership

- Create organizations table with Alembic migration (3-phase: create table, migrate data, drop old column)
- Add org_id FK on championships linking to organizations
- Refactor all schemas into one-class-per-file packages (auth, championship, organization, participant, registration, user)
- Update CRUD layer with selectinload for organization relationships
- Update frontend types and components to use nested organization object
- Remove phantom Championship fields (subtitle, venue, accent_color) from frontend

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

backend/app/schemas/registration/__init__.py

@@ -0,0 +1,13 @@
+from app.schemas.registration.create import RegistrationCreate
+from app.schemas.registration.update import RegistrationUpdate
+from app.schemas.registration.out import RegistrationOut
+from app.schemas.registration.list_item import RegistrationListItem
+from app.schemas.registration.with_user import RegistrationWithUser
+
+__all__ = [
+    "RegistrationCreate",
+    "RegistrationUpdate",
+    "RegistrationOut",
+    "RegistrationListItem",
+    "RegistrationWithUser",
+]

backend/app/schemas/registration/create.py

@@ -0,0 +1,10 @@
+import uuid
+
+from pydantic import BaseModel
+
+
+class RegistrationCreate(BaseModel):
+    championship_id: uuid.UUID
+    category: str | None = None
+    level: str | None = None
+    notes: str | None = None

backend/app/schemas/registration/list_item.py

@@ -0,0 +1,22 @@
+from datetime import datetime
+from typing import Any
+
+from pydantic import model_validator
+
+from app.schemas.registration.out import RegistrationOut
+
+
+class RegistrationListItem(RegistrationOut):
+    championship_title: str | None = None
+    championship_event_date: datetime | None = None
+    championship_location: str | None = None
+
+    @model_validator(mode="before")
+    @classmethod
+    def extract_championship(cls, data: Any) -> Any:
+        if hasattr(data, "championship") and data.championship:
+            champ = data.championship
+            data.__dict__["championship_title"] = champ.title
+            data.__dict__["championship_event_date"] = champ.event_date
+            data.__dict__["championship_location"] = champ.location
+        return data

backend/app/schemas/registration/out.py

@@ -0,0 +1,19 @@
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel
+
+
+class RegistrationOut(BaseModel):
+    model_config = {"from_attributes": True}
+
+    id: uuid.UUID
+    championship_id: uuid.UUID
+    user_id: uuid.UUID
+    category: str | None
+    level: str | None
+    notes: str | None
+    status: str
+    video_url: str | None
+    submitted_at: datetime
+    decided_at: datetime | None

backend/app/schemas/registration/update.py

@@ -0,0 +1,9 @@
+from pydantic import BaseModel
+
+
+class RegistrationUpdate(BaseModel):
+    status: str | None = None
+    video_url: str | None = None
+    category: str | None = None
+    level: str | None = None
+    notes: str | None = None

backend/app/schemas/registration/with_user.py

@@ -0,0 +1,6 @@
+from app.schemas.registration.out import RegistrationOut
+from app.schemas.user import UserOut
+
+
+class RegistrationWithUser(RegistrationOut):
+    user: UserOut