feat: Enhance Python environment setup with system Python option and improve dependency installation

refactor: Clean up imports in currencies and users routes
fix: Update theme settings saving logic and clean up test imports

scripts/backfill_currency.py

@@ -43,15 +43,14 @@ def backfill(
     engine = create_engine(db_url)
     with engine.begin() as conn:
         # Ensure currency table exists
-        res = (
+        if db_url.startswith("sqlite:"):
             conn.execute(
                 text(
                     "SELECT name FROM sqlite_master WHERE type='table' AND name='currency';"
                 )
             )
-            if db_url.startswith("sqlite:")
-            else conn.execute(text("SELECT to_regclass('public.currency');"))
-        )
+        else:
+            conn.execute(text("SELECT to_regclass('public.currency');"))
         # Note: we don't strictly depend on the above - we assume migration was already applied
 
         # Helper: find or create currency by code

scripts/seed_data.py

@@ -16,8 +16,7 @@ from __future__ import annotations
 
 import argparse
 import logging
-import os
-from typing import Iterable, Optional
+from typing import Optional
 
 import psycopg2
 from psycopg2 import errors