feat: strengthen backup and mobile workflows

tests/test_migration_backup_imports.py

@@ -0,0 +1,46 @@
+import os
+import sqlite3
+import subprocess
+from pathlib import Path
+
+
+def run_alembic(repo: Path, database: Path, *args: str) -> subprocess.CompletedProcess[str]:
+    env = os.environ.copy()
+    env["DODO_DATABASE_URL"] = f"sqlite+aiosqlite:///{database}"
+    return subprocess.run(
+        ["uv", "run", "alembic", *args], cwd=repo, env=env,
+        text=True, capture_output=True, check=False,
+    )
+
+
+def test_backup_migration_upgrade_downgrade_and_reupgrade(tmp_path):
+    repo = Path(__file__).resolve().parents[1]
+    database = tmp_path / "migration.sqlite3"
+    assert run_alembic(repo, database, "upgrade", "0018_task_completed_at").returncode == 0
+    upgraded = run_alembic(repo, database, "upgrade", "0019_backup_imports")
+    assert upgraded.returncode == 0, upgraded.stderr
+    with sqlite3.connect(database) as connection:
+        tables = {row[0] for row in connection.execute("select name from sqlite_master where type='table'")}
+        assert {"backup_imports", "backup_import_entities", "backup_preflights"} <= tables
+    downgraded = run_alembic(repo, database, "downgrade", "0018_task_completed_at")
+    assert downgraded.returncode == 0, downgraded.stderr
+    with sqlite3.connect(database) as connection:
+        tables = {row[0] for row in connection.execute("select name from sqlite_master where type='table'")}
+        assert "backup_imports" not in tables
+        assert "backup_import_entities" not in tables
+        assert "backup_preflights" not in tables
+    reupgraded = run_alembic(repo, database, "upgrade", "head")
+    assert reupgraded.returncode == 0, reupgraded.stderr
+
+
+def test_fresh_upgrade_has_single_head_and_backup_tables(tmp_path):
+    repo = Path(__file__).resolve().parents[1]
+    heads = run_alembic(repo, tmp_path / "unused.sqlite3", "heads")
+    assert heads.returncode == 0, heads.stderr
+    assert heads.stdout.count("(head)") == 1
+    database = tmp_path / "fresh.sqlite3"
+    upgraded = run_alembic(repo, database, "upgrade", "head")
+    assert upgraded.returncode == 0, upgraded.stderr
+    with sqlite3.connect(database) as connection:
+        tables = {row[0] for row in connection.execute("select name from sqlite_master where type='table'")}
+        assert {"backup_imports", "backup_import_entities", "backup_preflights"} <= tables