Rename the import package app to fluksio

A wheel whose top-level module is `app` collides with anything else in a
user's venv, so the package that is about to be published takes the name
it is published under. Only the Python package moves; the repo, the
Docker WORKDIR and the compose project keep theirs.

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

backend/fluksio/tests_pre_start.py

@@ -0,0 +1,39 @@
+import logging
+
+from sqlalchemy import Engine
+from sqlmodel import Session, select
+from tenacity import after_log, before_log, retry, stop_after_attempt, wait_fixed
+
+from fluksio.core.db import engine
+
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
+max_tries = 60 * 5  # 5 minutes
+wait_seconds = 1
+
+
+@retry(
+    stop=stop_after_attempt(max_tries),
+    wait=wait_fixed(wait_seconds),
+    before=before_log(logger, logging.INFO),
+    after=after_log(logger, logging.WARN),
+)
+def init(db_engine: Engine) -> None:
+    try:
+        # Try to create session to check if DB is awake
+        with Session(db_engine) as session:
+            session.exec(select(1))
+    except Exception as e:
+        logger.error(e)
+        raise e
+
+
+def main() -> None:
+    logger.info("Initializing service")
+    init(engine)
+    logger.info("Service finished initializing")
+
+
+if __name__ == "__main__":
+    main()