Harden location db startup validation

scripts/location_db_adopt.py

@@ -54,6 +54,30 @@ def _location_table_exists(database_path: Path) -> bool:
         conn.close()
 
 
+def _alembic_version_table_exists(database_path: Path) -> bool:
+    conn = sqlite3.connect(database_path)
+    try:
+        row = conn.execute(
+            "SELECT 1 FROM sqlite_master WHERE type = 'table' AND name = 'alembic_version'"
+        ).fetchone()
+        return row is not None
+    finally:
+        conn.close()
+
+
+def _fetch_alembic_revision(database_path: Path) -> str:
+    conn = sqlite3.connect(database_path)
+    try:
+        row = conn.execute("SELECT version_num FROM alembic_version").fetchone()
+        if row is None:
+            raise LocationDatabaseAdoptionError(
+                "Alembic version table exists but contains no revision"
+            )
+        return row[0]
+    finally:
+        conn.close()
+
+
 def _fetch_location_table_info(database_path: Path) -> list[tuple]:
     conn = sqlite3.connect(database_path)
     try:
@@ -91,11 +115,44 @@ def validate_legacy_location_db(database_url: str) -> None:
         )
 
 
+def validate_location_runtime_db(database_url: str) -> None:
+    database_path = _database_path_from_url(database_url)
+    if not database_path.exists():
+        raise LocationDatabaseAdoptionError(
+            "Location DB file was not found. Run 'python scripts/location_db_adopt.py' "
+            "first to initialize or adopt the location DB before starting the app."
+        )
+
+    if not _alembic_version_table_exists(database_path):
+        raise LocationDatabaseAdoptionError(
+            "Location DB exists but is not yet Alembic-managed. Run "
+            "'python scripts/location_db_adopt.py' first to adopt the legacy DB "
+            "before starting the app."
+        )
+
+    current_revision = _fetch_alembic_revision(database_path)
+    if current_revision != LOCATION_BASELINE_REVISION:
+        raise LocationDatabaseAdoptionError(
+            "Location DB revision mismatch. Refusing to start the app: "
+            f"expected {LOCATION_BASELINE_REVISION}, got {current_revision}"
+        )
+
+
 def adopt_or_initialize_location_db(database_url: str) -> str:
     database_path = _database_path_from_url(database_url)
     alembic_config = _make_alembic_config(database_url)
 
     if database_path.exists():
+        if _alembic_version_table_exists(database_path):
+            current_revision = _fetch_alembic_revision(database_path)
+            if current_revision != LOCATION_BASELINE_REVISION:
+                raise LocationDatabaseAdoptionError(
+                    "Location DB is already Alembic-managed but revision does not match "
+                    f"the expected baseline: expected {LOCATION_BASELINE_REVISION}, "
+                    f"got {current_revision}"
+                )
+            return "already_managed"
+
         validate_legacy_location_db(database_url)
         command.stamp(alembic_config, LOCATION_BASELINE_REVISION)
         return "adopted"
@@ -110,6 +167,8 @@ def main() -> None:
     result = adopt_or_initialize_location_db(settings.location_database_url)
     if result == "initialized":
         print("Initialized a new location DB via Alembic upgrade head.")
+    elif result == "already_managed":
+        print("Location DB is already Alembic-managed at the expected baseline revision.")
     else:
         print("Validated legacy location DB and stamped Alembic baseline successfully.")