Refactor app menu sidebar

* Rename to "app menu" across code
* Move content to dedicated sections/components, introduce app menu links
* Use CSS variable for hover background color across the app

app/components/app-menu/settings.gjs

@@ -0,0 +1,78 @@
+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';
+import eq from 'ember-truth-helpers/helpers/eq';
+
+export default class AppMenuSettings extends Component {
+  @service settings;
+
+  @action
+  updateApi(event) {
+    this.settings.updateOverpassApi(event.target.value);
+  }
+
+  @action
+  toggleKinetic(event) {
+    this.settings.updateMapKinetic(event.target.value === 'true');
+  }
+
+  <template>
+    <div class="sidebar-header">
+      <button type="button" class="back-btn" {{on "click" @onBack}}>
+        <Icon @name="arrow-left" @size={{20}} @color="#333" />
+      </button>
+      <h2>Settings</h2>
+      <button type="button" class="close-btn" {{on "click" @onClose}}>
+        <Icon @name="x" @size={{20}} @color="#333" />
+      </button>
+    </div>
+
+    <div class="sidebar-content">
+      <section class="settings-section">
+        <div class="form-group">
+          <label for="map-kinetic">Map Inertia (Kinetic Panning)</label>
+          <select
+            id="map-kinetic"
+            class="form-control"
+            {{on "change" this.toggleKinetic}}
+          >
+            <option
+              value="true"
+              selected={{if this.settings.mapKinetic "selected"}}
+            >
+              On
+            </option>
+            <option
+              value="false"
+              selected={{unless this.settings.mapKinetic "selected"}}
+            >
+              Off
+            </option>
+          </select>
+        </div>
+        <div class="form-group">
+          <label for="overpass-api">Overpass API Provider</label>
+          <select
+            id="overpass-api"
+            class="form-control"
+            {{on "change" this.updateApi}}
+          >
+            {{#each this.settings.overpassApis as |api|}}
+              <option
+                value={{api.url}}
+                selected={{if
+                  (eq api.url this.settings.overpassApi)
+                  "selected"
+                }}
+              >
+                {{api.name}}
+              </option>
+            {{/each}}
+          </select>
+        </div>
+      </section>
+    </div>
+  </template>
+}