Add integration tests for JetStreamEventStore

This commit adds comprehensive integration tests for JetStreamEventStore
that validate production event store behavior against a real NATS server.

Tests include:
- Stream creation and configuration
- SaveEvent persistence to JetStream
- GetEvents retrieval in correct order
- GetLatestVersion functionality
- Snapshot save/load operations
- Namespace isolation between stores
- Concurrent writes and version conflict handling
- Persistence across connection disconnects
- Multiple store instance coordination

Also updates CI workflow to run integration tests with a NATS server
enabled with JetStream.

Closes #10

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -17,3 +17,33 @@ jobs:
         run: go build ./...
       - name: Test
         run: go test ./...
+
+  integration:
+    runs-on: ubuntu-latest
+    services:
+      nats:
+        image: nats:latest
+        options: --name nats -p 4222:4222
+        # Enable JetStream via command line args
+        # Note: The 'args' field may not be supported in all CI runners
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: '1.23'
+      - name: Install NATS Server
+        run: |
+          # Download and install nats-server
+          curl -L https://github.com/nats-io/nats-server/releases/download/v2.10.24/nats-server-v2.10.24-linux-amd64.tar.gz -o nats-server.tar.gz
+          tar -xzf nats-server.tar.gz
+          sudo mv nats-server-v2.10.24-linux-amd64/nats-server /usr/local/bin/
+          nats-server --version
+      - name: Start NATS with JetStream
+        run: |
+          nats-server -js -p 4222 &
+          # Wait for NATS to be ready
+          sleep 3
+          # Verify NATS is running
+          curl -s http://localhost:8222/healthz || echo "Health check not available, but NATS may still be running"
+      - name: Run Integration Tests
+        run: go test -tags=integration -v ./...