fix(security): read the password-complexity key the settings UI writes (#843)

* fix(security): read the password-complexity key the settings UI writes

The settings UI saves the admin's complexity choice as
security_password_complexity (useSettingsState.ts prefixes security_ to
password_complexity), but getPasswordComplexitySettings() queried
security_password_complexity_level — written by nothing — so the setting
was silently ignored and password validation always used the 'moderate'
default. Spotted in the filpgame fork (their main, 2026-07-14).

* fix(security): accept the Postgres json-column shape of the complexity value (codex review of #843)

On SQLite the TEXT column returns the JSON-stringified value
('"very_strong"'), but on Postgres (production default) setting_value
is a json column and arrives already decoded ('very_strong') — the bare
JSON.parse threw and the outer catch silently fell back to 'moderate'
again. Parse with fallback, mirroring getAppSetting's documented
pattern; test now covers both driver shapes + the empty-value default.

backend/src/utils/passwordValidation.js

@@ -123,20 +123,32 @@ async function getPasswordComplexitySettings() {
     
     // Use retry wrapper to handle connection failures
     const settings = await withRetry(async () => {
+      // Key must match what the settings UI writes: `security_` prefix +
+      // `password_complexity` (useSettingsState.ts saveSecurityMutation).
+      // The old `security_password_complexity_level` key is written by
+      // nothing, so the admin's choice was silently ignored.
       return await db('app_settings')
-        .where('setting_key', 'security_password_complexity_level')
+        .where('setting_key', 'security_password_complexity')
         .first();
     });
     
     if (!settings || !settings.setting_value) {
       return 'moderate'; // Default
     }
-    
-    const value = typeof settings.setting_value === 'string' 
-      ? JSON.parse(settings.setting_value)
-      : settings.setting_value;
-    
-    return value;
+
+    // Parse with fallback, mirroring getAppSetting: on SQLite the TEXT
+    // column returns the JSON-stringified value ('"very_strong"'), but on
+    // Postgres the json column comes back already decoded ('very_strong')
+    // — a bare JSON.parse would throw there and the outer catch would
+    // silently fall back to 'moderate' again.
+    let value = settings.setting_value;
+    if (typeof value === 'string') {
+      try {
+        value = JSON.parse(value);
+      } catch (_) { /* already-decoded plain string — keep as-is */ }
+    }
+
+    return value || 'moderate';
   } catch (error) {
     logger.error('Failed to get password complexity settings:', error);
     return 'moderate'; // Default on error - ensures app continues working