Remove curasoft references, rename to detective method

- PLAN.md: replace 'curasoft-detective' with 'detective method'
- README.md: replace curasoft-detective link with plain reference
- test_websearch.py: fix test domain from ticket.curasoft.de to example.com
- Rewrote git history with git-filter-repo to remove all traces

README.md

@@ -143,6 +143,6 @@ docker compose up brain-watch                  # auto re-index on change
   Neo4j + Qdrant + Matrix RAG brain
 - [agent-skills](https://github.com/eSlider/agent-skills) — upstream
   skills (`web-search`, `db-yaml`, …) that 2dph integrates
-- [detective](https://github.com/detective) — the two-source method
+- detective method — the two-source method
 
 See [PLAN.md](PLAN.md) for decisions, execution status, and v2 open questions.