fix(frontend): add autocomplete attrs to credential inputs

Silences browser accessibility warnings on the HA token, MQTT username,
and MQTT password fields. Uses new-password for the secret inputs to
discourage Chrome's site-password autofill from leaking into broker /
HA-token configuration.

server/src/ledgrab/templates/modals/ha-source-editor.html

@@ -40,7 +40,7 @@
                     </div>
                     <small class="input-hint" style="display:none" data-i18n="ha_source.token.hint">Long-Lived Access Token from HA (Profile > Security > Long-Lived Access Tokens)</small>
                     <small id="ha-source-token-hint" class="input-hint" style="display:none" data-i18n="ha_source.token.edit_hint">Leave blank to keep the current token</small>
-                    <input type="password" id="ha-source-token" placeholder="eyJ0eXAiOi...">
+                    <input type="password" id="ha-source-token" placeholder="eyJ0eXAiOi..." autocomplete="new-password">
                 </div>
 
                 <!-- SSL -->

server/src/ledgrab/templates/modals/mqtt-source-editor.html

@@ -45,7 +45,7 @@
                     <div class="label-row">
                         <label for="mqtt-source-username" data-i18n="mqtt_source.username">Username (optional):</label>
                     </div>
-                    <input type="text" id="mqtt-source-username" placeholder="">
+                    <input type="text" id="mqtt-source-username" placeholder="" autocomplete="username">
                 </div>
 
                 <!-- Password -->
@@ -54,7 +54,7 @@
                         <label for="mqtt-source-password" data-i18n="mqtt_source.password">Password (optional):</label>
                     </div>
                     <small id="mqtt-source-password-hint" class="input-hint" style="display:none" data-i18n="mqtt_source.password.edit_hint">Leave blank to keep the current password</small>
-                    <input type="password" id="mqtt-source-password" placeholder="">
+                    <input type="password" id="mqtt-source-password" placeholder="" autocomplete="new-password">
                 </div>
 
                 <!-- Client ID -->