feat(projekt-matching): auto-tag created opportunities, add German docs (S68)

Every opportunity created by the workflow now carries the CTag
"Auto: Durch Suchagent-Treffer erstellt" (id 6a83292a186dce7b2), set via
cTagsIds directly in the create POST. The tag id is resolved at runtime
by name (EspoClient.ensure_ctag, same pattern as team_id; self-healing
after a CRM rebuild); the read-back verification now also checks the tag.
No backfill: existing opportunities and the saved "Via cowork-api
erstellt" list filter are untouched.

Live-verified end to end: synthetic trigger mail, opportunity
6a832b8f29cc86bdf created with cTagsNames containing the tag (test
artifact removed afterwards). 65/65 pytest.

Also adds the complete German technical documentation of the workflow
(docs/projekt-matching-dokumentation.md, sections 1-13 + S68 appendix).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

projekt-matching/projektmatch/espocrm.py

@@ -74,6 +74,12 @@ class EspoClient:
                          json={"firstName": first, "lastName": last,
                                "accountId": account_id})["id"]
 
+    def ensure_ctag(self, name):
+        hits = self.search("CTag", "equals", "name", name)
+        if hits:
+            return hits[0]["id"]
+        return self._req("POST", "CTag", json={"name": name})["id"]
+
     def unique_opportunity_name(self, name):
         existing = {h["name"] for h in self.search(
             "Opportunity", "startsWith", "name", name, max_size=100)}