Add Forgejo Actions CI/CD, ruff linting, and test foundation

- .forgejo/workflows/ci.yml: fast checks on every push (TS typecheck,
  Python lint via ruff, pytest) — no Docker build, ~30s with cache
- .forgejo/workflows/build.yml: Docker build with registry-side layer
  caching + SSH deploy on main branch pushes only
- pyproject.toml: add ruff to dev deps, configure pytest and ruff rules
- tests/: conftest.py + first unit tests for _safe_filename (no DB needed)
- Makefile: add lint, fmt, typecheck, test, check targets for local use

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -25,7 +25,26 @@ dependencies = [
 dev = [
     "pytest>=8.0",
     "pytest-asyncio>=0.23",
+    "ruff>=0.6",
 ]
 
 [tool.setuptools.packages.find]
 where = ["src"]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+testpaths = ["tests"]
+
+[tool.ruff]
+line-length = 120
+target-version = "py312"
+
+[tool.ruff.lint]
+# E = pycodestyle errors, F = pyflakes (catches unused imports, undefined names)
+# Start conservative — add more rules as the codebase gains coverage.
+select = ["E", "F"]
+ignore = [
+    "E501",  # line too long — long lines are acceptable in this codebase
+    "E402",  # module-level import not at top — common in Quart app factories
+    "F401",  # imported but unused — some re-exports are intentional
+]