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

decnet/ttp/base.py

@@ -41,6 +41,7 @@ KNOWN_SOURCE_KINDS: Final[frozenset[str]] = frozenset({
     "session",
     "http_request",
     "http_fingerprint",
+    "ipv6_leak",
 })