Auto-stamp or migrate on startup

On boot, run_migrations() checks the Alembic revision:
- no revision + tables exist  → stamp head (db.sql was run manually)
- no revision + no tables     → upgrade head (fresh install)
- revision present            → upgrade head (no-op if already current)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/db.py

@@ -1,8 +1,14 @@
+import logging
 import os
 
-from sqlalchemy import create_engine, text
+from alembic import command
+from alembic.config import Config
+from alembic.runtime.migration import MigrationContext
+from sqlalchemy import create_engine, inspect, text
 from sqlalchemy.orm import Session, sessionmaker
 
+logger = logging.getLogger("pops")
+
 
 def _db_url() -> str:
     return (
@@ -24,6 +30,21 @@ def get_db():
         db.close()
 
 
+def run_migrations() -> None:
+    alembic_cfg = Config("alembic.ini")
+    with engine.connect() as conn:
+        current_rev = MigrationContext.configure(conn).get_current_revision()
+    if current_rev is None:
+        if "printers" in inspect(engine).get_table_names():
+            logger.info("Existing schema detected, stamping Alembic to head")
+            command.stamp(alembic_cfg, "head")
+        else:
+            logger.info("Fresh database, running migrations")
+            command.upgrade(alembic_cfg, "head")
+    else:
+        command.upgrade(alembic_cfg, "head")
+
+
 def check_db() -> tuple[bool, str]:
     try:
         with engine.connect() as conn: