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/models/page_config.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+from datetime import datetime
+from typing import Optional
+
+from sqlalchemy import Integer, String, Text, DateTime, func, JSON, text
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from shared.db.base import Base
+
+
+class PageConfig(Base):
+    __tablename__ = "page_configs"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+
+    container_type: Mapped[str] = mapped_column(
+        String(32), nullable=False, server_default=text("'page'"),
+    )
+    container_id: Mapped[int] = mapped_column(Integer, nullable=False)
+
+    features: Mapped[dict] = mapped_column(
+        JSON, nullable=False, server_default="{}"
+    )
+
+    # Per-page SumUp credentials (NULL until configured)
+    sumup_merchant_code: Mapped[Optional[str]] = mapped_column(String(64), nullable=True)
+    sumup_api_key: Mapped[Optional[str]] = mapped_column(Text(), nullable=True)
+    sumup_checkout_prefix: Mapped[Optional[str]] = mapped_column(String(64), nullable=True)
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
+    deleted_at: Mapped[Optional[datetime]] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )