feat: enhance error handling and configuration validation

- Added a global exception handler to log unhandled exceptions and return a generic 500 JSON response without exposing details to the client.
- Updated the configuration to validate the `DATABASE_URL` format, ensuring it starts with `sqlite://` or `postgresql://`, and log warnings for invalid formats.
- Introduced safe parsing for numeric environment variables (`HTTP_PORT`, `INIT_DATA_MAX_AGE_SECONDS`) with defaults on invalid values, including logging warnings for out-of-range values.
- Enhanced the duty schedule parser to enforce limits on the number of schedule rows and the length of full names and duty strings, raising appropriate errors when exceeded.
- Updated internationalization messages to include generic error responses for import failures and parsing issues, improving user experience.
- Added unit tests to verify the new error handling and configuration validation behaviors.

tests/test_config.py

@@ -91,3 +91,29 @@ def test_require_bot_token_does_not_raise_when_set(monkeypatch):
     """require_bot_token() does nothing when BOT_TOKEN is set."""
     monkeypatch.setattr(config, "BOT_TOKEN", "123:ABC")
     config.require_bot_token()
+
+
+def test_settings_from_env_invalid_http_port_uses_default(monkeypatch):
+    """Invalid HTTP_PORT (non-numeric or out of range) yields default or clamped value."""
+    monkeypatch.delenv("HTTP_PORT", raising=False)
+    settings = config.Settings.from_env()
+    assert 1 <= settings.http_port <= 65535
+
+    monkeypatch.setenv("HTTP_PORT", "not-a-number")
+    settings = config.Settings.from_env()
+    assert settings.http_port == 8080
+
+    monkeypatch.setenv("HTTP_PORT", "0")
+    settings = config.Settings.from_env()
+    assert settings.http_port == 1
+
+    monkeypatch.setenv("HTTP_PORT", "99999")
+    settings = config.Settings.from_env()
+    assert settings.http_port == 65535
+
+
+def test_settings_from_env_invalid_init_data_max_age_uses_default(monkeypatch):
+    """Invalid INIT_DATA_MAX_AGE_SECONDS yields default 0."""
+    monkeypatch.setenv("INIT_DATA_MAX_AGE_SECONDS", "invalid")
+    settings = config.Settings.from_env()
+    assert settings.init_data_max_age_seconds == 0