feat: yoloVisibility config, alwaysShowLabel on groups, site settings panel

- AppConfig gains yoloVisibility: 'auto' | 'never' (default: auto)
- Group gains alwaysShowLabel?: boolean
- YOLO toggle only renders when showYoloToggle is true (auto + >1 group)
- Group divider shows when >1 group OR alwaysShowLabel is set
- New /admin/api/config GET+PUT endpoint for yolo settings
- Admin: alwaysShowLabel checkbox in group form
- Admin: ⚙ Settings panel with YOLO label, description, and visibility controls

src/routes/admin/+page.svelte

@@ -7,7 +7,7 @@
 
   // ── State ────────────────────────────────────────────────────────────────────
   let unitsData = $state<UnitsData>({ units: [], groups: [] });
-  let selectedItem = $state<{ type: 'unit' | 'group'; id: string } | null>(null);
+  let selectedItem = $state<{ type: 'unit' | 'group' | 'settings'; id: string } | null>(null);
   let checkedUnitIds = $state<Set<string>>(new Set());
   let bulkAction = $state<string>('');         // '' | 'move' | 'delete'
   let bulkMoveTargetGroupId = $state<string>('');
@@ -32,6 +32,50 @@
   let groupFormSnapshot = $state<Partial<Group>>({});
   let groupFieldError = $state<string | null>(null); // which field has error
 
+  // Site config state
+  let configYoloLabel = $state('YOLO mode');
+  let configYoloDescription = $state('(cross-group conversions)');
+  let configYoloVisibility = $state<'auto' | 'never'>('auto');
+  let configSaving = $state(false);
+  let configError = $state<string | null>(null);
+  let configSuccess = $state<string | null>(null);
+
+  async function loadConfig() {
+    const res = await fetch(`${api}/config`);
+    if (!res.ok) return;
+    const c = await res.json();
+    configYoloLabel = c.yoloLabel ?? 'YOLO mode';
+    configYoloDescription = c.yoloDescription ?? '(cross-group conversions)';
+    configYoloVisibility = c.yoloVisibility ?? 'auto';
+  }
+
+  async function saveConfig() {
+    configSaving = true;
+    configError = null;
+    configSuccess = null;
+    try {
+      const res = await fetch(`${api}/config`, {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({
+          yoloLabel: configYoloLabel,
+          yoloDescription: configYoloDescription,
+          yoloVisibility: configYoloVisibility,
+        })
+      });
+      if (!res.ok) { configError = 'Save failed'; }
+      else { configSuccess = 'Saved.'; }
+    } catch { configError = 'Network error'; }
+    configSaving = false;
+  }
+
+  function onConfigKeydown(e: KeyboardEvent) {
+    if (e.key === 'Enter' && (e.target as HTMLElement).tagName !== 'TEXTAREA') {
+      e.preventDefault();
+      saveConfig();
+    }
+  }
+
   // ── Auto-ID state ─────────────────────────────────────────────────────────────
   let unitIdManuallyEdited = $state(false);
   let groupIdManuallyEdited = $state(false);
@@ -195,7 +239,7 @@
     expandedGroups = new Set([...expandedGroups, ...groups.map((g) => g.id)]);
   }
 
-  $effect(() => { loadData(); });
+  $effect(() => { loadData(); loadConfig(); });
 
   async function extractError(res: Response, fallback: string): Promise<string> {
     const body = await res.json().catch(() => ({}));
@@ -842,6 +886,7 @@
     <div class="tree-footer">
       <button onclick={() => startNewUnit()}>+ Add Unit</button>
       <button class="outline" onclick={startNewGroup}>+ Add Group</button>
+      <button class="outline secondary" onclick={() => { selectedItem = { type: 'settings', id: 'settings' }; }}>⚙ Settings</button>
     </div>
   </aside>
 
@@ -953,6 +998,10 @@
           <option value="alpha">Alphabetical</option>
         </select>
       </label>
+      <label class="checkbox-label">
+        <input type="checkbox" bind:checked={groupForm.alwaysShowLabel} />
+        <span>Always show group label</span>
+      </label>
       <label class="checkbox-label">
         <input type="checkbox" bind:checked={groupForm.hidden} />
         <span>Don't show on front end</span>
@@ -971,6 +1020,35 @@
       </div>
       </div><!-- /onkeydown group form -->
 
+    {:else if selectedItem?.type === 'settings'}
+      <!-- svelte-ignore a11y_no_static_element_interactions -->
+      <div onkeydown={onConfigKeydown}>
+        <h3>Site Settings</h3>
+        {#if configError}<p class="form-msg form-error" role="alert">{configError}</p>{/if}
+        {#if configSuccess}<p class="form-msg form-success" role="status">{configSuccess}</p>{/if}
+        <fieldset>
+          <legend>YOLO Mode Toggle</legend>
+          <label>
+            Label
+            <input type="text" bind:value={configYoloLabel} placeholder="YOLO mode" />
+          </label>
+          <label>
+            Description <small class="muted">(shown inline after label)</small>
+            <input type="text" bind:value={configYoloDescription} placeholder="(cross-group conversions)" />
+          </label>
+          <label>
+            Visibility
+            <select bind:value={configYoloVisibility}>
+              <option value="auto">Auto — show when more than one group is present</option>
+              <option value="never">Never — always hidden</option>
+            </select>
+          </label>
+        </fieldset>
+        <div class="form-actions">
+          <button onclick={saveConfig} disabled={configSaving}>{configSaving ? 'Saving…' : 'Save'}</button>
+        </div>
+      </div>
+
     {:else}
       <p class="select-hint">Select a unit or group to edit, or add a new one.</p>
     {/if}