fix: resolve issues #194, #195, #196, #197

- #194: Send full date format object instead of just format string to prevent JSON parse errors
- #195: Remove non-functional forgot password link, fix README port 3005 -> 3000
- #196: Use ADMIN_PASSWORD env var in migration, update existing user in create-admin script instead of failing
- #197: Convert camelCase filter keys to snake_case in photo export to match backend PhotoFilterBuilder

frontend/src/features/settings/hooks/useSettingsState.ts

@@ -256,11 +256,7 @@ export function useSettingsState() {
     mutationFn: async () => {
       const settingsData: Record<string, unknown> = {};
       Object.entries(generalSettings).forEach(([key, value]) => {
-        if (key === 'date_format' && typeof value === 'object' && value.format) {
-          settingsData[`general_${key}`] = value.format;
-        } else {
-          settingsData[`general_${key}`] = value;
-        }
+        settingsData[`general_${key}`] = value;
       });
       return settingsService.updateSettings(settingsData);
     },