refactor(assets): database layer — split queries into modules and merge migrations

- Split monolithic queries.py into modular query modules (asset, asset_reference, common, tags)
- Absorb bulk_ops.py and tags.py into query modules
- Merge migrations 0002-0005 into single migration (0002_merge_to_asset_references)
- Update models.py (merge AssetInfo/AssetCacheState into AssetReference)
- Enable SQLite foreign key enforcement
- Add comprehensive query-layer tests

Co-authored-by: Amp <amp@ampcode.com>
Amp-Thread-ID: https://ampcode.com/threads/T-019c917d-82b5-7448-a04f-9cd59c69d0a2

app/assets/database/queries/common.py

@@ -0,0 +1,40 @@
+"""Shared utilities for database query modules."""
+
+from typing import Iterable
+
+import sqlalchemy as sa
+
+from app.assets.database.models import AssetReference
+
+MAX_BIND_PARAMS = 800
+
+
+def calculate_rows_per_statement(cols: int) -> int:
+    """Calculate how many rows can fit in one statement given column count."""
+    return max(1, MAX_BIND_PARAMS // max(1, cols))
+
+
+def iter_chunks(seq, n: int):
+    """Yield successive n-sized chunks from seq."""
+    for i in range(0, len(seq), n):
+        yield seq[i : i + n]
+
+
+def iter_row_chunks(rows: list[dict], cols_per_row: int) -> Iterable[list[dict]]:
+    """Yield chunks of rows sized to fit within bind param limits."""
+    if not rows:
+        return
+    rows_per_stmt = calculate_rows_per_statement(cols_per_row)
+    for i in range(0, len(rows), rows_per_stmt):
+        yield rows[i : i + rows_per_stmt]
+
+
+def build_visible_owner_clause(owner_id: str) -> sa.sql.ClauseElement:
+    """Build owner visibility predicate for reads.
+
+    Owner-less rows are visible to everyone.
+    """
+    owner_id = (owner_id or "").strip()
+    if owner_id == "":
+        return AssetReference.owner_id == ""
+    return AssetReference.owner_id.in_(["", owner_id])