fix: simplify Docker build to resolve multi-platform failures

## Root cause
- Docker buildx memory options were incorrectly formatted
- Database build during Docker image creation was failing on multi-platform builds
- n8n native dependencies caused issues across different architectures

## Solution
- Removed invalid buildx driver-opts configuration
- Eliminated database build stage from Dockerfile
- Now using pre-built nodes.db file (11MB) from repository
- Fixed .dockerignore to include nodes.db in build context
- Added .dockerignore to version control (was incorrectly gitignored)

## Benefits
- Faster builds (no n8n package installation during build)
- More reliable multi-platform builds (amd64 + arm64)
- Simpler Dockerfile (3 stages instead of 4)

Database can still be rebuilt locally using 'npm run rebuild' when needed.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.github/workflows/docker-build.yml

@@ -34,10 +34,6 @@ jobs:
       - name: Set up Docker Buildx
         id: buildx
         uses: docker/setup-buildx-action@v3
-        with:
-          driver-opts: |
-            memory=8g
-            memory-swap=16g
         
       - name: Log in to GitHub Container Registry
         if: github.event_name != 'pull_request'
@@ -74,9 +70,6 @@ jobs:
           build-args: |
             BUILDKIT_INLINE_CACHE=1
           provenance: false
-          # Add build constraints to prevent OOM
-          builder: ${{ steps.buildx.outputs.name }}
-          no-cache-filters: db-builder
 
   # Nginx build commented out until Phase 2
   # build-nginx: