Add Forgejo Actions CI workflow

Runs cargo fmt/clippy/test/audit via the existing cargo-make ci task on every push and pull request.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.forgejo/workflows/ci.yml

@@ -0,0 +1,35 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  ci:
+    runs-on: docker
+    container: rust:latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/bin
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Install toolchain components
+        run: rustup component add clippy rustfmt
+
+      - name: Install cargo-make and cargo-audit
+        run: |
+          for crate in cargo-make cargo-audit; do
+            command -v "$crate" >/dev/null 2>&1 || cargo install "$crate"
+          done
+
+      - name: Run CI checks
+        run: cargo make ci