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

bin/tools/web-search/test_websearch.py

@@ -76,7 +76,7 @@ class PhiGuard(unittest.TestCase):
 
     def test_plain_technical_query_passes(self):
         self.assertIsNone(ws.phi_reason("Pflegegrad SGB XI Einstufung"))
-        self.assertIsNone(ws.phi_reason("site:ticket.detective.de Toureffizienz"))
+        self.assertIsNone(ws.phi_reason("site:example.com technical query"))
 
     def test_long_digit_run_is_refused(self):
         self.assertIsNotNone(ws.phi_reason("Kunde 4711220385 Adresse"))