refactor: streamline configuration loading and enhance admin checks

- Refactored the configuration loading in `config.py` to utilize a single source of truth through the `Settings` class, improving maintainability and clarity.
- Introduced the `is_admin_for_telegram_user` function in `repository.py` to centralize admin checks based on usernames and phone numbers.
- Updated command handlers to use the new admin check function, ensuring consistent access control across the application.
- Enhanced error handling in the `error_handler` to log exceptions when sending error replies to users, improving debugging capabilities.
- Improved the handling of user phone updates in `repository.py` to ensure proper normalization and validation of phone numbers.

duty_teller/handlers/import_duty_schedule.py

@@ -7,6 +7,7 @@ from telegram import Update
 from telegram.ext import CommandHandler, ContextTypes, MessageHandler, filters
 
 from duty_teller.db.session import session_scope
+from duty_teller.db.repository import is_admin_for_telegram_user
 from duty_teller.i18n import get_lang, t
 from duty_teller.importers.duty_schedule import (
     DutyScheduleParseError,
@@ -23,7 +24,13 @@ async def import_duty_schedule_cmd(
     if not update.message or not update.effective_user:
         return
     lang = get_lang(update.effective_user)
-    if not config.is_admin(update.effective_user.username or ""):
+
+    def check_admin() -> bool:
+        with session_scope(config.DATABASE_URL) as session:
+            return is_admin_for_telegram_user(session, update.effective_user.id)
+
+    is_admin_user = await asyncio.get_running_loop().run_in_executor(None, check_admin)
+    if not is_admin_user:
         await update.message.reply_text(t(lang, "import.admin_only"))
         return
     context.user_data["awaiting_handover_time"] = True
@@ -38,7 +45,13 @@ async def handle_handover_time_text(
         return
     if not context.user_data.get("awaiting_handover_time"):
         return
-    if not config.is_admin(update.effective_user.username or ""):
+
+    def check_admin() -> bool:
+        with session_scope(config.DATABASE_URL) as session:
+            return is_admin_for_telegram_user(session, update.effective_user.id)
+
+    is_admin_user = await asyncio.get_running_loop().run_in_executor(None, check_admin)
+    if not is_admin_user:
         return
     lang = get_lang(update.effective_user)
     text = update.message.text.strip()
@@ -63,7 +76,15 @@ async def handle_duty_schedule_document(
         return
     lang = get_lang(update.effective_user)
     handover = context.user_data.get("handover_utc_time")
-    if not handover or not config.is_admin(update.effective_user.username or ""):
+    if not handover:
+        return
+
+    def check_admin() -> bool:
+        with session_scope(config.DATABASE_URL) as session:
+            return is_admin_for_telegram_user(session, update.effective_user.id)
+
+    is_admin_user = await asyncio.get_running_loop().run_in_executor(None, check_admin)
+    if not is_admin_user:
         return
     if not (update.message.document.file_name or "").lower().endswith(".json"):
         await update.message.reply_text(t(lang, "import.need_json"))