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/main.py

@@ -1,5 +1,6 @@
 import logging
 import os
+from collections.abc import AsyncGenerator
 from contextlib import asynccontextmanager
 
 from fastapi import FastAPI, Request, status
@@ -53,7 +54,7 @@ setup_logging()
 _IS_PRODUCTION = os.environ.get("AEGIS_ENV", "").lower() == "production"
 
 @asynccontextmanager
-async def lifespan(app: FastAPI):
+async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
     """Startup / shutdown logic."""
     ensure_bucket_exists()
     start_scheduler()
@@ -124,7 +125,7 @@ app.include_router(osint_router.router, prefix="/api/v1")
 
 
 @app.get("/health", include_in_schema=False)
-def health():
+def health() -> dict[str, str]:
     """Minimal health check — returns only an HTTP 200 with no service metadata.
 
     Access is restricted to internal networks at the Nginx level
@@ -149,7 +150,7 @@ def _serialize_validation_errors(exc: RequestValidationError) -> list[dict]:
 
 
 @app.exception_handler(RequestValidationError)
-async def validation_exception_handler(request: Request, exc: RequestValidationError):
+async def validation_exception_handler(request: Request, exc: RequestValidationError) -> JSONResponse:
     """Handle validation errors with consistent format."""
     return JSONResponse(
         status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
@@ -162,7 +163,7 @@ async def validation_exception_handler(request: Request, exc: RequestValidationE
 
 
 @app.exception_handler(SQLAlchemyError)
-async def sqlalchemy_exception_handler(request: Request, exc: SQLAlchemyError):
+async def sqlalchemy_exception_handler(request: Request, exc: SQLAlchemyError) -> JSONResponse:
     """Handle database errors."""
     logging.error(f"Database error: {exc}")
     return JSONResponse(
@@ -175,7 +176,7 @@ async def sqlalchemy_exception_handler(request: Request, exc: SQLAlchemyError):
 
 
 @app.exception_handler(Exception)
-async def general_exception_handler(request: Request, exc: Exception):
+async def general_exception_handler(request: Request, exc: Exception) -> JSONResponse:
     """Handle all unhandled exceptions."""
     logging.error(f"Unhandled exception: {exc}")
     return JSONResponse(