feat: add test data cleanup endpoint

Add POST /maintenance/cleanup/test-data endpoint to purge LLM test data
from wiki, graph, and vectors. Security-restricted to test user namespace
only (users/llm-tester/*, users/llm_tester/*).

- Supports dry_run=true (default) to preview before deleting
- Cleans vectors, graph nodes, and wiki pages
- Scheduler task configured for weekly cleanup (Sunday 3:00 AM)

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

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

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "library-desk"
-version = "1.4.3"
+version = "1.4.4"
 description = "Coordination service for The Library system - HybridRAG queries, document ingestion, entity extraction, and knowledge consolidation"
 readme = "README.md"
 requires-python = ">=3.12"