T10.3 fix - the drop migration was deleting every project membership

Found by actually seeding the pre-migration schema and rolling forward, rather
than by checking that the column disappeared. The column disappeared correctly;
project_members came back empty.

batch_alter_table emulates ALTER on SQLite by rebuilding the table - create a
new one, copy the rows, DROP the original, rename. server/alembic/env.py:22
imports the engine from server/db.py, which registers a connect listener
setting PRAGMA foreign_keys=ON, so that DROP TABLE cascaded through
project_members.user_id (ondelete="CASCADE") and took every membership row with
it. No error, nothing in the log, and the users table looked perfect
afterwards.

Production would have escaped it - Postgres does a real ALTER TABLE DROP COLUMN
and touches nothing else - so this was a local-dev and test-fixture data loss,
which is worse in one specific way: the tests CLAUDE.md requires run against a
throwaway SQLite database, so the suite would have been validating behaviour
against silently emptied membership tables.

Wrapping the batch in PRAGMA foreign_keys=OFF is not the fix: that pragma is a
no-op inside a transaction and alembic runs migrations in one. The rebuild is
simply unnecessary - SQLite has had native ALTER TABLE DROP COLUMN since 3.35
(2021), this runtime has 3.42, and Postgres has always had it. Plain
op.drop_column touches one table and cascades nowhere.

The reasoning is written into the migration's docstring as a DO NOT, because
batch_alter_table is the reflexive thing to reach for when a migration has to
work on SQLite and the failure is invisible.

Re-verified with memberships in the fixture:

  3/3 users survive, roles intact (admin still admin)
  2/2 project_members survive
  downgrade -1 -> column back, nullable; upgrade -> gone again

Also closed BL-026: notify.send_now removed. Nothing referenced it and its
docstring described itself entirely in terms of password resets. send_email,
which it wrapped, is untouched and still used by the outbox.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

server/alembic/versions/b7e4f1a20c93_drop_user_password_hash.py

@@ -15,6 +15,23 @@ The column is recreated NULLABLE on downgrade, deliberately. The baseline schema
 declared it NOT NULL, but there are no values to put back, so a NOT NULL column
 with no server default would refuse to add itself on any table that has rows.
 
+DO NOT WRAP THIS IN batch_alter_table. An earlier version of this migration did,
+and it silently deleted every row of `project_members` on SQLite.
+
+Why: alembic's batch mode emulates ALTER on SQLite by rebuilding the table —
+create a new one, copy the rows, DROP the original, rename. `server/alembic/env.py`
+imports the engine from `server/db.py`, which registers a `connect` listener setting
+`PRAGMA foreign_keys=ON`, so that DROP TABLE cascades through
+`project_members.user_id`, which is declared `ondelete="CASCADE"`. Every project
+membership in the database goes with it, with no error and nothing in the log.
+
+Turning the pragma off around the batch is not a fix either: `PRAGMA foreign_keys`
+is a no-op inside a transaction, and alembic runs migrations in one.
+
+The real answer is that the rebuild is unnecessary. SQLite gained native
+ALTER TABLE ... DROP COLUMN in 3.35 (2021); this runtime has 3.42 and Postgres has
+always had it. A plain drop_column touches one table and cascades nowhere.
+
 Revision ID: b7e4f1a20c93
 Revises: a1b8c6d4e2f9
 Create Date: 2026-08-21
@@ -29,14 +46,11 @@ depends_on = None
 
 
 def upgrade():
-    # batch_alter_table for SQLite's benefit: it has no DROP COLUMN before 3.35,
-    # so alembic rebuilds the table. Postgres drops it directly. Local dev runs on
-    # SQLite and production on Postgres, so this has to work on both.
-    with op.batch_alter_table('users') as batch:
-        batch.drop_column('password_hash')
+    # Plain, un-batched, on both engines. See the docstring: batching this destroys
+    # project_members on SQLite.
+    op.drop_column('users', 'password_hash')
 
 
 def downgrade():
-    with op.batch_alter_table('users') as batch:
-        batch.add_column(sa.Column('password_hash', sa.String(length=200),
-                                   nullable=True))
+    op.add_column('users', sa.Column('password_hash', sa.String(length=200),
+                                     nullable=True))