ci: add GitHub Actions CI workflow with just

Add CI workflow running build/lint checks for all components:
- backend: Go build + golangci-lint
- worker/swift: Go build + golangci-lint
- frontend: Biome + TypeScript + ESLint
- worker/php: Biome

Add `ci` recipes to each justfile so GHA uses `just ci` uniformly.

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

5 files changed, 80 insertions, 0 deletions

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..6937620
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,64 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  backend:
+    name: Backend
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: backend/go.mod
+      - uses: extractions/setup-just@v2
+      - run: just ci
+        working-directory: backend
+
+  worker-swift:
+    name: Worker (Swift)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: worker/swift/go.mod
+      - uses: extractions/setup-just@v2
+      - run: just ci
+        working-directory: worker/swift
+
+  frontend:
+    name: Frontend
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+          cache-dependency-path: frontend/package-lock.json
+      - uses: extractions/setup-just@v2
+      - run: npm ci
+        working-directory: frontend
+      - run: just ci
+        working-directory: frontend
+
+  worker-php:
+    name: Worker (PHP)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+          cache-dependency-path: worker/php/package-lock.json
+      - uses: extractions/setup-just@v2
+      - run: npm ci
+        working-directory: worker/php
+      - run: just ci
+        working-directory: worker/php
diff --git a/backend/justfile b/backend/justfile
index 4207b92..a74047f 100644
--- a/backend/justfile
+++ b/backend/justfile
@@ -2,5 +2,7 @@ check:
     go build -o /dev/null ./...
     go tool golangci-lint run
 
+ci: check
+
 gen:
     go generate ./...
diff --git a/frontend/justfile b/frontend/justfile
new file mode 100644
index 0000000..beba8b3
--- /dev/null
+++ b/frontend/justfile
@@ -0,0 +1,7 @@
+check:
+    npm run check
+
+ci:
+    npx biome ci .
+    npx tsc --noEmit
+    npx eslint .
diff --git a/worker/php/justfile b/worker/php/justfile
new file mode 100644
index 0000000..115165d
--- /dev/null
+++ b/worker/php/justfile
@@ -0,0 +1,5 @@
+check:
+    npm run check
+
+ci:
+    npx biome ci .
diff --git a/worker/swift/justfile b/worker/swift/justfile
index 33cf92c..b203597 100644
--- a/worker/swift/justfile
+++ b/worker/swift/justfile
@@ -1,3 +1,5 @@
 check:
     go build -o /dev/null ./...
     go tool golangci-lint run
+
+ci: check