test: add characterization tests for core modules

33 tests covering env/io helpers, config parsers, pipeline meta I/O,
worker inbox logic, and FastAPI smoke routes. No gmic/rembg subprocesses.

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitea/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+
+jobs:
+  lint-and-test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements-dev.txt
+
+      - name: Ruff lint
+        run: ruff check app/ tests/
+
+      - name: Ruff format check
+        run: ruff format --check app/ tests/
+
+      - name: Pytest
+        run: pytest -q