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>

.dockerignore

@@ -0,0 +1,52 @@
+# .dockerignore
+node_modules
+npm-debug.log
+.git
+.gitignore
+.env
+.env.local
+# Keep nodes.db but exclude other database files
+data/*.db
+!data/nodes.db
+dist
+.DS_Store
+*.log
+coverage
+.nyc_output
+.vscode
+.idea
+*.swp
+*.swo
+*~
+docker-compose.override.yml
+.github
+docs
+tests
+jest.config.js
+.eslintrc.js
+*.md
+!README.md
+!LICENSE
+# Exclude n8n-docs if present
+../n8n-docs
+n8n-docs
+# Exclude extracted nodes
+extracted-nodes/
+# Exclude temp directory
+temp/
+# Exclude any backup or temporary files
+*.bak
+*.tmp
+*.temp
+# Exclude build artifacts
+build/
+out/
+# Exclude local development files
+.eslintcache
+.stylelintcache
+# Exclude any large test data
+test-data/
+# Exclude Docker files during build
+Dockerfile*
+docker-compose*.yml
+.dockerignore