refactor: rename functions to verb-based naming convention

Rename functions across app/assets/ to follow verb-based naming:
- is_scalar → check_is_scalar
- project_kv → expand_metadata_to_rows
- _visible_owner_clause → _build_visible_owner_clause
- _chunk_rows → _iter_row_chunks
- _at_least_one → _validate_at_least_one_field
- _tags_norm → _normalize_tags_field
- _ser_dt → _serialize_datetime
- _ser_updated → _serialize_updated_at
- _error_response → _build_error_response
- _validation_error_response → _build_validation_error_response
- file_sender → stream_file_chunks
- seed_assets_endpoint → seed_assets
- utcnow → get_utc_now
- _safe_sort_field → _validate_sort_field
- _safe_filename → _sanitize_filename
- fast_asset_file_check → check_asset_file_fast
- prefixes_for_root → get_prefixes_for_root
- blake3_hash → compute_blake3_hash
- blake3_hash_async → compute_blake3_hash_async
- _is_within → _check_is_within
- _rel → _compute_relative

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests-unit/assets_test/queries/test_cache_state.py

@@ -15,7 +15,7 @@ from app.assets.database.queries import (
     bulk_insert_cache_states_ignore_conflicts,
     get_cache_states_by_paths_and_asset_ids,
 )
-from app.assets.helpers import pick_best_live_path, utcnow
+from app.assets.helpers import pick_best_live_path, get_utc_now
 
 
 def _make_asset(session: Session, hash_val: str | None = None, size: int = 1024) -> Asset:
@@ -228,7 +228,7 @@ class TestGetOrphanedSeedAssetIds:
 class TestDeleteAssetsByIds:
     def test_deletes_assets_and_infos(self, session: Session):
         asset = _make_asset(session, "hash1")
-        now = utcnow()
+        now = get_utc_now()
         info = AssetInfo(
             owner_id="", name="test", asset_id=asset.id,
             created_at=now, updated_at=now, last_access_time=now
@@ -325,7 +325,7 @@ class TestDeleteCacheStatesByIds:
 class TestDeleteOrphanedSeedAsset:
     def test_deletes_seed_asset_and_infos(self, session: Session):
         asset = _make_asset(session, hash_val=None)
-        now = utcnow()
+        now = get_utc_now()
         info = AssetInfo(
             owner_id="", name="test", asset_id=asset.id,
             created_at=now, updated_at=now, last_access_time=now