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>

src/routers/wiki.py

@@ -229,7 +229,7 @@ async def smart_create_page(
             content_extractor=content_extractor,
             settings=settings
         )
-        wiki_page_writer = WikiPageWriter(ollama_client=ollama_client)
+        wiki_page_writer = WikiPageWriter(ollama_client=ollama_client, settings=settings)
 
         # Step 1-5: Research + Generate + Create page
         page, research_data = await wiki_service.smart_create_page(