feat: Phase 3 campaign management

Campaign CRUD API with cascading delete across all campaign-scoped
tables, a systems endpoint to seed the create-campaign form, active
campaign state wired to the sidebar chaos factor, and a campaign
management view for creating/switching/deleting campaigns.

public/index.html

@@ -28,6 +28,8 @@
         </button>
       </div>
 
+      <div class="sidebar-active-campaign" id="activeCampaignName">No active campaign</div>
+
       <nav class="sidebar-nav">
         <div class="nav-section">
           <div class="nav-section-label">Oracle</div>
@@ -147,4 +149,5 @@
   </div>
 </body>
 <script src="js/app.js" type="module"></script>
+<script src="js/campaigns.js" type="module"></script>
 </html>