Monorepo: consolidate 7 repos into one

Combines shared, blog, market, cart, events, federation, and account
into a single repository. Eliminates submodule sync, sibling model
copying at build time, and per-app CI orchestration.

Changes:
- Remove per-app .git, .gitmodules, .gitea, submodule shared/ dirs
- Remove stale sibling model copies from each app
- Update all 6 Dockerfiles for monorepo build context (root = .)
- Add build directives to docker-compose.yml
- Add single .gitea/workflows/ci.yml with change detection
- Add .dockerignore for monorepo build context
- Create __init__.py for federation and account (cross-app imports)

shared/alembic/versions/0011_add_entry_tickets.py

@@ -0,0 +1,43 @@
+"""Add ticket_price and ticket_count to calendar_entries
+
+Revision ID: 0011_add_entry_tickets
+Revises: 0010_add_post_likes
+Create Date: 2025-12-07 14:00:00.000000
+"""
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import NUMERIC
+
+# revision identifiers, used by Alembic.
+revision = "0011_add_entry_tickets"
+down_revision = "0010_add_post_likes"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # Add ticket_price column (nullable - NULL means no tickets)
+    op.add_column(
+        "calendar_entries",
+        sa.Column(
+            "ticket_price",
+            NUMERIC(10, 2),
+            nullable=True,
+        ),
+    )
+
+    # Add ticket_count column (nullable - NULL means unlimited)
+    op.add_column(
+        "calendar_entries",
+        sa.Column(
+            "ticket_count",
+            sa.Integer(),
+            nullable=True,
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("calendar_entries", "ticket_count")
+    op.drop_column("calendar_entries", "ticket_price")