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/6cb124491c9d_entry_posts.py

@@ -0,0 +1,36 @@
+
+# Alembic migration script template
+
+"""Add calendar_entry_posts association table
+
+Revision ID: 6cb124491c9d
+Revises: 0011_add_entry_tickets
+Create Date: 2025-12-07 03:40:49.194068
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import TIMESTAMP
+
+# revision identifiers, used by Alembic.
+revision = '6cb124491c9d'
+down_revision = '0011_add_entry_tickets'
+branch_labels = None
+depends_on = None
+
+def upgrade() -> None:
+    op.create_table(
+        'calendar_entry_posts',
+        sa.Column('id', sa.Integer(), primary_key=True, autoincrement=True),
+        sa.Column('entry_id', sa.Integer(), sa.ForeignKey('calendar_entries.id', ondelete='CASCADE'), nullable=False),
+        sa.Column('post_id', sa.Integer(), sa.ForeignKey('posts.id', ondelete='CASCADE'), nullable=False),
+        sa.Column('created_at', TIMESTAMP(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.Column('deleted_at', TIMESTAMP(timezone=True), nullable=True),
+    )
+    op.create_index('ix_entry_posts_entry_id', 'calendar_entry_posts', ['entry_id'])
+    op.create_index('ix_entry_posts_post_id', 'calendar_entry_posts', ['post_id'])
+
+def downgrade() -> None:
+    op.drop_index('ix_entry_posts_post_id', 'calendar_entry_posts')
+    op.drop_index('ix_entry_posts_entry_id', 'calendar_entry_posts')
+    op.drop_table('calendar_entry_posts')