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/0007_add_oid_entries.py

@@ -0,0 +1,50 @@
+from alembic import op
+import sqlalchemy as sa
+
+revision = "0007_add_oid_entries"
+down_revision = "0006_update_calendar_entries"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # Add order_id column
+    op.add_column(
+        "calendar_entries",
+        sa.Column("order_id", sa.Integer(), nullable=True),
+    )
+    op.create_foreign_key(
+        "fk_calendar_entries_order_id",
+        "calendar_entries",
+        "orders",
+        ["order_id"],
+        ["id"],
+        ondelete="SET NULL",
+    )
+    op.create_index(
+        "ix_calendar_entries_order_id",
+        "calendar_entries",
+        ["order_id"],
+        unique=False,
+    )
+
+    # Optional: add an index on state if you want faster queries by state
+    op.create_index(
+        "ix_calendar_entries_state",
+        "calendar_entries",
+        ["state"],
+        unique=False,
+    )
+
+
+def downgrade():
+    # Drop indexes and FK in reverse order
+    op.drop_index("ix_calendar_entries_state", table_name="calendar_entries")
+
+    op.drop_index("ix_calendar_entries_order_id", table_name="calendar_entries")
+    op.drop_constraint(
+        "fk_calendar_entries_order_id",
+        "calendar_entries",
+        type_="foreignkey",
+    )
+    op.drop_column("calendar_entries", "order_id")