style(api): complete the S1a import-order fix (R6 S1a follow-up)

Round-1 review finding #4 named only audit.py/plex.py, but the same misplaced
`from app.utils import iso` sat in channels/downloads/feed/notifications too — the
round missed them (ruff enforces no import order here, so the gate was silent).
Move them to alphabetical position for consistency. No behaviour change.

backend/app/routes/channels.py

@@ -11,7 +11,6 @@ from sqlalchemy.orm import Session
 from app import quota, sysconfig
 from app.auth import current_user, require_human, require_write_scope
 from app.db import get_db
-from app.utils import iso
 from app.models import (
     LIVE_OR_UPCOMING,
     BlockedChannel,
@@ -29,6 +28,7 @@ from app.routes.admin import admin_user
 from app.sync.explore import explore_ingest_page
 from app.sync.runner import run_recent_backfill
 from app.sync.subscriptions import apply_channel_details
+from app.utils import iso
 from app.youtube.client import YouTubeClient, YouTubeError
 
 router = APIRouter(prefix="/api/channels", tags=["channels"])

backend/app/routes/downloads.py

@@ -18,7 +18,6 @@ from app import sysconfig
 from app.auth import admin_user, require_human
 from app.config import settings
 from app.db import get_db
-from app.utils import iso
 from app.downloads import edit as editmod
 from app.downloads import links as linksmod
 from app.downloads import formats, quota, service, storage
@@ -33,6 +32,7 @@ from app.models import (
 )
 from app.security import hash_password
 from app.userscope import is_messageable_user, messageable_clauses
+from app.utils import iso
 
 router = APIRouter(prefix="/api/downloads", tags=["downloads"])
 admin_router = APIRouter(prefix="/api/admin/downloads", tags=["admin-downloads"])

backend/app/routes/feed.py

@@ -13,7 +13,6 @@ from sqlalchemy.orm.exc import StaleDataError
 from app import quota
 from app.auth import current_user
 from app.db import get_db
-from app.utils import iso
 from app.models import (
     LIVE_OR_UPCOMING,
     BlockedChannel,
@@ -30,6 +29,7 @@ from app.models import (
     VideoState,
 )
 from app.sync.videos import parse_iso8601_duration
+from app.utils import iso
 from app.youtube.client import YouTubeClient, YouTubeError
 
 router = APIRouter(prefix="/api", tags=["feed"])

backend/app/routes/notifications.py

@@ -11,8 +11,8 @@ from sqlalchemy.orm import Session
 from app.auth import current_user
 from app.db import get_db
 from app.models import Notification, User
-from app.utils import iso
 from app.notifications import trim_read
+from app.utils import iso
 
 router = APIRouter(prefix="/api/me/notifications", tags=["notifications"])