Refactor settings menu, add Nostr settings

Adds a setting to control if photos should be uploaded only to the
main/default server, or all known servers of a user.

Only upload to the main server by default, to speed up adding photos.

app/components/app-menu/settings/nostr.gjs

@@ -0,0 +1,53 @@
+import Component from '@glimmer/component';
+import { on } from '@ember/modifier';
+import { service } from '@ember/service';
+import { action } from '@ember/object';
+import Icon from '#components/icon';
+
+export default class AppMenuSettingsNostr extends Component {
+  @service settings;
+
+  @action
+  togglePhotoFallbackUploads(event) {
+    this.settings.updateNostrPhotoFallbackUploads(
+      event.target.value === 'true'
+    );
+  }
+
+  <template>
+    {{! template-lint-disable no-nested-interactive }}
+    <details>
+      <summary>
+        <Icon @name="zap" @size={{20}} />
+        <span>Nostr</span>
+      </summary>
+      <div class="details-content">
+        <div class="form-group">
+          <label for="nostr-photo-fallback-uploads">Upload photos to fallback
+            servers</label>
+          <select
+            id="nostr-photo-fallback-uploads"
+            class="form-control"
+            {{on "change" this.togglePhotoFallbackUploads}}
+          >
+            <option
+              value="true"
+              selected={{if this.settings.nostrPhotoFallbackUploads "selected"}}
+            >
+              Yes
+            </option>
+            <option
+              value="false"
+              selected={{unless
+                this.settings.nostrPhotoFallbackUploads
+                "selected"
+              }}
+            >
+              No
+            </option>
+          </select>
+        </div>
+      </div>
+    </details>
+  </template>
+}