refactor(types): add comprehensive type annotations across backend Python codebase

Enable ANN rules in ruff.toml (flake8-annotations) and resolve all 221 violations:

ANN201/ANN202 — return types on 168 public/private functions:
- All 28 FastAPI routers: endpoints annotated with dict/list/specific schema/
  StreamingResponse/FileResponse/JSONResponse as appropriate
- main.py: lifespan→AsyncGenerator[None,None], exception handlers→JSONResponse
- database.py: get_db→Generator[Session,None,None], proxy methods→correct types
- middleware/request_context.py: dispatch→Response with Callable call_next type

ANN001/ANN002/ANN003 — 32 missing argument types:
- seed_demo.py: all db parameters typed as Session
- domain/unit_of_work.py: __aexit__ exc_type/exc_val/exc_tb typed with TracebackType
- services: audit_service user_id→UUID|None, heatmap_service query/model/builder,
  notification_service test→Test, tempo_service test→Test/user→User,
  test_workflow_service test_id→UUID, campaign_crud **fields→object,
  test_crud **fields→object (4 sites)

ANN401 — 16 Any usages resolved:
- Domain entities (campaign/technique/threat_actor/test_entity): replaced Any with
  actual ORM types via TYPE_CHECKING guards to avoid circular imports
- detection_rule_service: test_id/detection_rule_id/evaluator_id→UUID
- score_cache: kept Any with # noqa: ANN401 (genuinely generic cache)
- jira_service/tempo_service: kept Any with # noqa: ANN401 (lazy optional deps)
- d3fend_import_service: _to_str(v: Any) kept with # noqa: ANN401

ANN204/ANN205/ANN206 — special/static/class methods:
- database.py proxy __call__/__getattr__: *args: object/**kwargs: object
- schemas/test.py model_validate: obj→object, **kwargs→object
- sa_technique_repository._int_type→type

All 439 unit tests pass. ruff check app/ → All checks passed!

backend/app/routers/jira.py

@@ -29,7 +29,7 @@ def search_issues(
     q: str = Query(..., min_length=2),
     max_results: int = Query(10, le=50),
     user: User = Depends(get_current_user),
-):
+) -> list[JiraIssueResult]:
     """Search Jira issues by JQL or free text."""
     return jira_service.search_jira_issues(q, max_results)
 
@@ -39,7 +39,7 @@ def create_link(
     body: JiraLinkCreate,
     db: Session = Depends(get_db),
     user: User = Depends(get_current_user),
-):
+) -> JiraLinkOut:
     """Associate an Aegis entity with a Jira issue."""
     with UnitOfWork(db) as uow:
         link = jira_service.create_link(
@@ -74,7 +74,7 @@ def list_links(
     entity_id: Optional[UUID] = None,
     db: Session = Depends(get_db),
     user: User = Depends(get_current_user),
-):
+) -> list[JiraLinkOut]:
     """List Jira links, optionally filtered by entity."""
     return jira_service.list_links(
         db,
@@ -88,7 +88,7 @@ def sync_link(
     link_id: UUID,
     db: Session = Depends(get_db),
     user: User = Depends(require_role("admin")),
-):
+) -> dict:
     """Force bidirectional sync for a specific Jira link."""
     with UnitOfWork(db) as uow:
         link = jira_service.get_link_or_raise(db, link_id)
@@ -102,7 +102,7 @@ def delete_link(
     link_id: UUID,
     db: Session = Depends(get_db),
     user: User = Depends(get_current_user),
-):
+) -> None:
     """Remove a Jira link."""
     with UnitOfWork(db) as uow:
         link = jira_service.delete_link(db, link_id)
@@ -123,7 +123,7 @@ def create_issue_from_entity(
     entity_id: UUID,
     db: Session = Depends(get_db),
     user: User = Depends(get_current_user),
-):
+) -> dict:
     """Auto-create a Jira issue from an Aegis entity and link them."""
     with UnitOfWork(db) as uow:
         result = jira_service.create_issue_and_link(