feat(tests): richer server-side filters + true total count for GET /tests

GET /tests caps limit at 200, so any page relying on len(results) for a
"total" count (e.g. Validated Tests) silently under-reports once there
are more matches than the page size — the 200 shown was a page cap, not
the real total.

- Adds GET /tests/count, sharing its query-building with list_tests()
  via a new _build_test_query() so the two can't drift apart.
- Adds technique_search (free-text on MITRE ID or name), attack_success,
  detection_result, and validated_from/validated_to filters, so callers
  aren't limited to state/technique_id/platform/creator.

backend/app/routers/tests.py

@@ -118,6 +118,11 @@ from app.services.test_crud_service import (
     list_tests as crud_list_tests,
 )
 
+# Import  from app.services.test_crud_service
+from app.services.test_crud_service import (
+    count_tests as crud_count_tests,
+)
+
 # Import  from app.services.test_crud_service
 from app.services.test_crud_service import (
     update_test as crud_update_test,
@@ -203,13 +208,14 @@ def _mask_for_team_blindness(test_out: TestOut, *, viewer_role: str) -> TestOut:
 # ---------------------------------------------------------------------------
 
 
-@router.get("", response_model=list[TestOut])
-# Define function list_tests
-def list_tests(
+def _test_list_filter_params(
     # Entry: state
     state: Optional[str] = Query(None, description="Filter by test state"),
     # Entry: technique_id
     technique_id: Optional[uuid.UUID] = Query(None, description="Filter by technique"),
+    technique_search: Optional[str] = Query(
+        None, description="Free-text filter on technique MITRE ID or name"
+    ),
     # Entry: platform
     platform: Optional[str] = Query(None, description="Filter by platform"),
     # Entry: created_by
@@ -225,6 +231,52 @@ def list_tests(
     not_in_any_campaign: bool = Query(
         False, description="Only return tests not linked to any campaign"
     ),
+    attack_success: Optional[str] = Query(None, description="Filter by attack success outcome"),
+    detection_result: Optional[str] = Query(None, description="Filter by detection outcome"),
+    validated_from: Optional[datetime] = Query(
+        None, description="Only tests validated on/after this date"
+    ),
+    validated_to: Optional[datetime] = Query(
+        None, description="Only tests validated on/before this date"
+    ),
+) -> dict:
+    """Shared filter params for GET /tests and GET /tests/count, so the two
+    endpoints can never silently drift out of sync with each other."""
+    return {
+        "state": state,
+        "technique_id": technique_id,
+        "technique_search": technique_search,
+        "platform": platform,
+        "created_by": created_by,
+        "pending_validation_side": pending_validation_side,
+        "reviewer_id": reviewer_id,
+        "not_in_any_campaign": not_in_any_campaign,
+        "attack_success": attack_success,
+        "detection_result": detection_result,
+        "validated_from": validated_from,
+        "validated_to": validated_to,
+    }
+
+
+@router.get("/count")
+def count_tests(
+    filters: dict = Depends(_test_list_filter_params),
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+) -> dict:
+    """Return the true total of tests matching the given filters.
+
+    GET /tests caps `limit` at 200, so pages that show "N results" need
+    this to report the real total rather than len(page) — which silently
+    under-reports whenever there are more matches than the page size.
+    """
+    return {"total": crud_count_tests(db, **filters)}
+
+
+@router.get("", response_model=list[TestOut])
+# Define function list_tests
+def list_tests(
+    filters: dict = Depends(_test_list_filter_params),
     offset: int = Query(0, ge=0),
     # Entry: limit
     limit: int = Query(50, ge=1, le=200),
@@ -236,12 +288,7 @@ def list_tests(
     """Return a paginated list of tests, optionally filtered by state, technique, platform or creator.
 
     Args:
-        state (Optional[str]): Filter by test state (e.g. ``draft``, ``validated``).
-        technique_id (Optional[uuid.UUID]): Filter tests belonging to a specific technique.
-        platform (Optional[str]): Filter by target platform (e.g. ``windows``, ``linux``).
-        created_by (Optional[uuid.UUID]): Filter by the UUID of the creator.
-        pending_validation_side (Optional[str]): Filter ``in_review`` tests pending validation
-            on ``'red'`` or ``'blue'`` side.
+        filters (dict): Shared filter params — see ``_test_list_filter_params``.
         offset (int): Number of records to skip for pagination.
         limit (int): Maximum number of records to return.
         db (Session): SQLAlchemy database session.
@@ -253,18 +300,7 @@ def list_tests(
     # Return crud_list_tests(
     return crud_list_tests(
         db,
-        # Keyword argument: state
-        state=state,
-        # Keyword argument: technique_id
-        technique_id=technique_id,
-        # Keyword argument: platform
-        platform=platform,
-        # Keyword argument: created_by
-        created_by=created_by,
-        # Keyword argument: pending_validation_side
-        pending_validation_side=pending_validation_side,
-        reviewer_id=reviewer_id,
-        not_in_any_campaign=not_in_any_campaign,
+        **filters,
         offset=offset,
         # Keyword argument: limit
         limit=limit,