feat: add reusable CI/CD pipeline templates

Reusable Gitea Actions workflows for lint, test, build, and deploy:
- lint-python, lint-node, lint-rust
- test-python, test-node, test-rust
- build-push (Docker build + push to Gitea registry)
- deploy-k8s (GitOps image tag update in cluster repo)

Plus example caller workflows for python-fullstack, rust-service,
and node-frontend stacks. Branch refs aligned to staging per CON-570 standards.

.gitea/workflows/lint-python.yaml

@@ -0,0 +1,37 @@
+# Reusable workflow: Python linting with Ruff
+# Usage: uses: wectrl-net/ci-templates/.gitea/workflows/lint-python.yaml@main
+name: Lint Python (Ruff)
+
+on:
+  workflow_call:
+    inputs:
+      python-version:
+        description: "Python version to use"
+        required: false
+        type: string
+        default: "3.13"
+      ruff-version:
+        description: "Ruff version constraint"
+        required: false
+        type: string
+        default: ">=0.9.0"
+      working-directory:
+        description: "Directory containing the Python project"
+        required: false
+        type: string
+        default: "."
+
+jobs:
+  lint:
+    name: Ruff
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ inputs.python-version }}
+      - name: Install Ruff
+        run: pip install "ruff${{ inputs.ruff-version }}"
+      - name: Run Ruff
+        run: ruff check --output-format=github .
+        working-directory: ${{ inputs.working-directory }}