add new flag to disable some future features and make some updates to chat ux

frontend/src/routes/admin/+page.svelte

@@ -188,6 +188,20 @@
 							</button>
 						</form>
 					</div>
+					<div class="flag-row">
+						<span class="flag-name">rewardsTargets</span>
+						<span class="flag-desc">Multi-target reward rules (Competition / Collaboration)</span>
+						<form method="POST" action="?/togglePlatformFlag" use:enhance>
+							<input type="hidden" name="flag" value="rewardsTargets" />
+							<button
+								type="submit"
+								class="toggle-btn"
+								class:active={page.data.platformFlags?.rewardsTargets}
+							>
+								{page.data.platformFlags?.rewardsTargets ? 'ON' : 'OFF'}
+							</button>
+						</form>
+					</div>
 				</Card>
 			</CardGrid>
 
@@ -923,6 +937,11 @@
 		font-size: 0.85rem;
 		color: #374151;
 	}
+	.flag-desc {
+		font-size: 0.7rem;
+		color: #9ca3af;
+		text-align: center;
+	}
 
 	.toggle-btn {
 		background: #e5e7eb;