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>

.gitignore

@@ -51,7 +51,6 @@ coverage/
 .yarn-integrity
 
 # Docker
-.dockerignore
 docker-compose.override.yml
 
 # Miscellaneous