feat: add optional vector database and semantic search to helm chart

Add support for deploying Qdrant vector database and Ollama embedding
service as optional helm chart dependencies. Enables semantic search
capabilities for Nextcloud content with flexible deployment options.

Chart Dependencies:
- Add Qdrant v0.9.0 from qdrant/qdrant-helm (conditional)
- Add Ollama v1.33.0 from otwld/ollama-helm (conditional)
- Both dependencies only deploy when enabled

Configuration (values.yaml):
- vectorSync: Background sync settings (interval, workers, queue size)
- qdrant: Subchart config with persistence, resources, clustering
- ollama: Subchart config with model pull, persistence, resources
  - Support for external Ollama via ollama.url (no subchart deployment)
- openai: Alternative embedding provider (OpenAI or compatible API)

Environment Variables (deployment.yaml):
- VECTOR_SYNC_* variables when vectorSync.enabled
- QDRANT_URL, QDRANT_COLLECTION when qdrant.enabled
- OLLAMA_BASE_URL, OLLAMA_EMBEDDING_MODEL when ollama enabled or URL set
- OPENAI_API_KEY when openai.enabled

Documentation:
- README: New "Vector Search & Semantic Capabilities" section
- README: Example 5 showing three deployment patterns
- NOTES.txt: Conditional guidance when vector features enabled
- Secret template for OpenAI API key management

All features disabled by default for backward compatibility.
Tested with helm template and helm lint.

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

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

charts/nextcloud-mcp-server/.gitignore

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+charts/