fix: SQLite migration 0003 FK drop fails on file-backed DBs (MB-2)

Add naming_convention to Base.metadata so Alembic batch-mode reflection
can match unnamed FK constraints created by migration 0002. Pass
naming_convention and render_as_batch=True through env.py online config.

Add migration roundtrip tests (upgrade/downgrade/cycle from baseline).

Amp-Thread-ID: https://ampcode.com/threads/T-019ce466-1683-7471-b6e1-bb078223cda0
Co-authored-by: Amp <amp@ampcode.com>

alembic_db/env.py

@@ -8,7 +8,7 @@ from alembic import context
 config = context.config
 
 
-from app.database.models import Base
+from app.database.models import Base, NAMING_CONVENTION
 target_metadata = Base.metadata
 
 # other values from the config, defined by the needs of env.py,
@@ -51,7 +51,10 @@ def run_migrations_online() -> None:
 
     with connectable.connect() as connection:
         context.configure(
-            connection=connection, target_metadata=target_metadata
+            connection=connection,
+            target_metadata=target_metadata,
+            render_as_batch=True,
+            naming_convention=NAMING_CONVENTION,
         )
 
         with context.begin_transaction():

alembic_db/versions/0003_add_metadata_prompt.py

@@ -10,6 +10,8 @@ Create Date: 2026-03-09
 from alembic import op
 import sqlalchemy as sa
 
+from app.database.models import NAMING_CONVENTION
+
 revision = "0003_add_metadata_prompt"
 down_revision = "0002_merge_to_asset_references"
 branch_labels = None
@@ -29,7 +31,9 @@ def upgrade() -> None:
     # Existing values are asset-content IDs that won't match reference IDs,
     # so null them out first.
     op.execute("UPDATE asset_references SET preview_id = NULL WHERE preview_id IS NOT NULL")
-    with op.batch_alter_table("asset_references") as batch_op:
+    with op.batch_alter_table(
+        "asset_references", naming_convention=NAMING_CONVENTION
+    ) as batch_op:
         batch_op.drop_constraint(
             "fk_asset_references_preview_id_assets", type_="foreignkey"
         )
@@ -43,7 +47,9 @@ def upgrade() -> None:
 
 
 def downgrade() -> None:
-    with op.batch_alter_table("asset_references") as batch_op:
+    with op.batch_alter_table(
+        "asset_references", naming_convention=NAMING_CONVENTION
+    ) as batch_op:
         batch_op.drop_constraint(
             "fk_asset_references_preview_id_asset_references", type_="foreignkey"
         )