feat(ttp): E.1.10 repository contract — TTPMixin with insert_tags + list_techniques_by_{identity,attacker,campaign,session} + list_distinct_techniques

Empty NotImplementedError bodies; the SQL lands at E.3 implementation.
Mixin composed onto SQLModelRepository alongside the existing domain
mixins. Dialect-specific INSERT-OR-IGNORE syntax overrides land in
the per-backend subclasses at E.3 per the dual-DB-backend convention.

decnet/web/db/sqlmodel_repo/__init__.py

@@ -49,6 +49,7 @@ from decnet.web.db.sqlmodel_repo.realism import RealismMixin
 from decnet.web.db.sqlmodel_repo.swarm import SwarmMixin
 from decnet.web.db.sqlmodel_repo.topology import TopologyMixin
 from decnet.web.db.sqlmodel_repo.tarpit import TarpitMixin
+from decnet.web.db.sqlmodel_repo.ttp import TTPMixin
 from decnet.web.db.sqlmodel_repo.webhooks import WebhooksMixin
 
 
@@ -69,6 +70,7 @@ class SQLModelRepository(
     SwarmMixin,
     TarpitMixin,
     TopologyMixin,
+    TTPMixin,
     WebhooksMixin,
     BaseRepository,
 ):