refactor: consolidate Ollama model configuration

- Add OLLAMA_EMBEDDING_MODEL for embeddings (nomic-embed-text)
- OLLAMA_MODEL now used for all LLM operations (mistral-nemo-large:latest)
- Remove separate reranker_model setting
- Update WikiPageWriter to use settings instead of hardcoded model
- Improves VRAM efficiency by keeping one model hot

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

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

README.md

@@ -49,7 +49,8 @@ QDRANT_PORT=6333
 WIKIJS_URL=http://wiki:3000
 SEARXNG_URL=http://searxng:8080
 OLLAMA_URL=http://ollama:11434
-OLLAMA_MODEL=nomic-embed-text
+OLLAMA_MODEL=mistral-nemo-large:latest
+OLLAMA_EMBEDDING_MODEL=nomic-embed-text
 REDIS_HOST=redis-shared
 REDIS_PORT=6379
 REDIS_DB=2