feat: Add phoenixd mnemonic display (#3931)

Co-authored-by: alan <alan@lnbits.com>

lnbits/static/i18n/en.js

@@ -275,6 +275,8 @@ window.localisation.en = {
   requires_server_restart:
     'Changing these settings requires a server restart to take effect.',
   funding_source_info: 'Select the active funding wallet',
+  phoenixd_warning:
+    "Phoenixd mnemonic is only available if phoenixd data-dir is specified and is readable by LNbits. It's not indicative of phoenixd not running. It just means LNbits cannot access the mnemonic to display it here.",
   latest_update: 'You are on the latest version {version}.',
   notifications: 'Notifications',
   notifications_configure: 'Configure Notifications',

lnbits/static/js/components/admin/lnbits-admin-funding-sources.js

@@ -202,7 +202,18 @@ window.app.component('lnbits-admin-funding-sources', {
           'Phoenixd',
           {
             phoenixd_api_endpoint: 'Endpoint',
-            phoenixd_api_password: 'Key'
+            phoenixd_api_password: 'Key',
+            phoenixd_data_dir: {
+              label: 'Data Directory',
+              hint: 'Directory where phoenixd stores its data, including the seed phrase.'
+            },
+            phoenixd_mnemonic: {
+              label: 'Phoenixd Seed Phrase',
+              hint: 'Only available if phoenixd data-dir is specified',
+              readonly: true,
+              copy: true,
+              qrcode: true
+            }
           }
         ],
         [