ui: добавить поиск, фильтрацию и сортировку на списки

API:
- scans.py: добавить search, status, sort_by, sort_dir параметры
- packages.py: добавить search, sort_by, sort_dir параметры
- web/routes.py: передать новые параметры в шаблоны

UI:
- scans_list.html: search input (htmx debounce), status filter dropdown,
  sortable columns с hx-get, empty state
- packages_list.html: search input (htmx debounce), sortable columns,
  empty state
- pagination сохраняет все параметры фильтрации/сортировки

guarddog_nexus/api/scans.py

@@ -10,18 +10,47 @@ from guarddog_nexus.models import Finding, Scan
 
 router = APIRouter(prefix="/api/v1/scans", tags=["scans"])
 
+VALID_SORT_FIELDS = {
+    "id": Scan.id,
+    "package_name": Scan.package_name,
+    "started_at": Scan.started_at,
+    "status": Scan.status,
+    "total_findings": Scan.total_findings,
+    "flagged": Scan.flagged,
+}
+
 
 @router.get("")
 async def list_scans(
     limit: int = Query(50, le=200),
     offset: int = Query(0, ge=0),
     flagged: bool | None = Query(None),
+    search: str | None = Query(None),
+    status: str | None = Query(None),
+    repository: str | None = Query(None),
+    sort_by: str = Query("started_at"),
+    sort_dir: str = Query("desc"),
     session: AsyncSession = Depends(get_session),
 ):
     q = select(Scan)
+
     if flagged is not None:
         q = q.where(Scan.flagged == flagged)
-    q = q.order_by(Scan.started_at.desc()).offset(offset).limit(limit)
+    if status:
+        q = q.where(Scan.status == status)
+    if repository:
+        q = q.where(Scan.repository == repository)
+    if search:
+        pattern = f"%{search}%"
+        q = q.where(
+            Scan.package_name.ilike(pattern) | Scan.package_version.ilike(pattern)
+        )
+
+    sort_field = VALID_SORT_FIELDS.get(sort_by, Scan.started_at)
+    sort_dir = "asc" if sort_dir.lower() == "asc" else "desc"
+    q = q.order_by(sort_field.desc() if sort_dir == "desc" else sort_field.asc())
+
+    q = q.offset(offset).limit(limit)
 
     total = await session.scalar(select(func.count(Scan.id)))