ci: add GitHub Actions CI for public credibility badge

Lean self-contained workflow — no Forgejo-specific secrets.
circuitforge-core installs from Forgejo git (public repo).
Forgejo (.forgejo/workflows/ci.yml) remains the canonical CI.

Backend: ruff + pytest | Frontend: vue-tsc + vitest

.github/workflows/ci.yml

@@ -0,0 +1,56 @@
+# Peregrine CI — runs on GitHub mirror for public credibility badge.
+# Forgejo (.forgejo/workflows/ci.yml) is the canonical CI — keep these in sync.
+# No Forgejo-specific secrets used here; circuitforge-core is public on Forgejo.
+
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  backend:
+    name: Backend (Python)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+          cache: pip
+
+      - name: Install dependencies
+        run: pip install -r requirements.txt
+
+      - name: Lint
+        run: ruff check .
+
+      - name: Test
+        run: pytest tests/ -v --tb=short
+
+  frontend:
+    name: Frontend (Vue)
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: web
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: npm
+          cache-dependency-path: web/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Type check
+        run: npx vue-tsc --noEmit
+
+      - name: Test
+        run: npm run test