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/requirements.txt

@@ -0,0 +1,49 @@
+starlette>=0.37,<0.39
+aiofiles==25.1.0
+aiohttp>=3.9
+aiosmtplib==5.0.0
+alembic==1.17.0
+anyio==4.11.0
+async-timeout==5.0.1
+asyncpg==0.30.0
+beautifulsoup4==4.14.2
+blinker==1.9.0
+Brotli==1.1.0
+certifi==2025.10.5
+click==8.3.0
+cryptography>=41.0
+exceptiongroup==1.3.0
+Flask==3.1.2
+greenlet==3.2.4
+h11==0.16.0
+h2==4.3.0
+hpack==4.1.0
+httpcore==1.0.9
+httpx==0.28.1
+Hypercorn==0.17.3
+hyperframe==6.1.0
+idna==3.10
+itsdangerous==2.2.0
+Jinja2==3.1.6
+lxml==6.0.2
+Mako==1.3.10
+MarkupSafe==3.0.3
+priority==2.0.0
+psycopg==3.2.11
+psycopg-binary==3.2.11
+PyJWT==2.10.1
+PyYAML==6.0.3
+Quart==0.20.0
+sniffio==1.3.1
+soupsieve==2.8
+SQLAlchemy==2.0.44
+taskgroup==0.2.2
+tomli==2.3.0
+typing_extensions==4.15.0
+Werkzeug==3.1.3
+wsproto==1.2.0
+zstandard==0.25.0
+redis>=5.0
+mistune>=3.0
+pytest>=8.0
+pytest-asyncio>=0.23