feat(ttp/ipv6_leak): wire Ipv6LeakLifter into composite tagger and worker

- Add "ipv6_leak" to KNOWN_SOURCE_KINDS in ttp/base.py
- Register Ipv6LeakLifter(store) in factory.py get_tagger()
- Subscribe worker to attacker.fingerprinted; route by Event.type
  so JARM/HASSH/ipv6_leak share the topic without source_kind collision
- Add bump_attacker_ipv6_leak() to BaseRepository (abstract) +
  TTPMixin (implementation): increments ipv6_leak_count, sets last_ipv6_*
  denorm fields, appends-with-dedup to AttackerIdentity.ipv6_link_local_iids
- Call bump_attacker_ipv6_leak from _process_event after insert_tags
- Add DummyRepo stub + coverage call in tests/db/test_base_repo.py

tests/db/test_base_repo.py

@@ -136,6 +136,8 @@ class DummyRepo(BaseRepository):
         await super().list_tags_by_scope_and_technique(**kw); return []
     async def list_distinct_techniques(self):
         await super().list_distinct_techniques(); return []
+    async def bump_attacker_ipv6_leak(self, attacker_uuid, identity_uuid, evidence):
+        await super().bump_attacker_ipv6_leak(attacker_uuid, identity_uuid, evidence)
     async def list_ttp_tags_by_attacker(self, uuid, limit=2000):
         return []
     async def list_attacker_commands_deduped(self, uuid):
@@ -289,6 +291,8 @@ async def test_base_repo_coverage():
         )
     with pytest.raises(NotImplementedError):
         await dr.list_distinct_techniques()
+    with pytest.raises(NotImplementedError):
+        await dr.bump_attacker_ipv6_leak("uuid-1", None, {})
     with pytest.raises(NotImplementedError):
         from decnet.web.db.repository import BaseRepository
         await BaseRepository.list_ttp_tags_by_attacker(dr, "a")