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/alembic/versions/a1b2c3d4e5f6_add_organizations_table.py

@@ -0,0 +1,86 @@
+"""add organizations table and championship ownership
+
+Revision ID: a1b2c3d4e5f6
+Revises: 43d947192af5
+Create Date: 2026-03-01 18:00:00.000000
+
+"""
+import uuid
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'a1b2c3d4e5f6'
+down_revision: Union[str, None] = '43d947192af5'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Phase 1: Create organizations table
+    op.create_table('organizations',
+        sa.Column('id', sa.Uuid(), nullable=False),
+        sa.Column('user_id', sa.Uuid(), nullable=False),
+        sa.Column('name', sa.String(length=255), nullable=False),
+        sa.Column('instagram', sa.String(length=100), nullable=True),
+        sa.Column('email', sa.String(length=255), nullable=True),
+        sa.Column('city', sa.String(length=100), nullable=True),
+        sa.Column('logo_url', sa.String(length=500), nullable=True),
+        sa.Column('verified', sa.Boolean(), nullable=False),
+        sa.Column('status', sa.String(length=20), nullable=False),
+        sa.Column('block_reason', sa.String(length=500), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=False),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=False),
+        sa.ForeignKeyConstraint(['user_id'], ['users.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id'),
+        sa.UniqueConstraint('user_id'),
+    )
+
+    # Phase 1b: Add org_id to championships
+    with op.batch_alter_table('championships') as batch_op:
+        batch_op.add_column(sa.Column('org_id', sa.Uuid(), nullable=True))
+        batch_op.create_foreign_key('fk_championships_org_id', 'organizations', ['org_id'], ['id'], ondelete='SET NULL')
+
+    # Phase 2: Migrate existing organizer data to organizations table
+    conn = op.get_bind()
+    rows = conn.execute(
+        sa.text("SELECT id, organization_name FROM users WHERE role = 'organizer' AND organization_name IS NOT NULL")
+    ).fetchall()
+    for row in rows:
+        org_id = str(uuid.uuid4())
+        conn.execute(
+            sa.text(
+                "INSERT INTO organizations (id, user_id, name, verified, status, created_at, updated_at) "
+                "VALUES (:id, :user_id, :name, 0, 'active', CURRENT_TIMESTAMP, CURRENT_TIMESTAMP)"
+            ),
+            {"id": org_id, "user_id": str(row[0]), "name": row[1]}
+        )
+
+    # Phase 3: Remove organization_name from users (keep instagram_handle)
+    with op.batch_alter_table('users') as batch_op:
+        batch_op.drop_column('organization_name')
+
+
+def downgrade() -> None:
+    # Re-add organization_name to users
+    with op.batch_alter_table('users') as batch_op:
+        batch_op.add_column(sa.Column('organization_name', sa.String(length=255), nullable=True))
+
+    # Migrate data back from organizations to users
+    conn = op.get_bind()
+    orgs = conn.execute(sa.text("SELECT user_id, name FROM organizations")).fetchall()
+    for org in orgs:
+        conn.execute(
+            sa.text("UPDATE users SET organization_name = :name WHERE id = :user_id"),
+            {"name": org[1], "user_id": str(org[0])}
+        )
+
+    # Remove org_id from championships
+    with op.batch_alter_table('championships') as batch_op:
+        batch_op.drop_constraint('fk_championships_org_id', type_='foreignkey')
+        batch_op.drop_column('org_id')
+
+    op.drop_table('organizations')