fix(discord): add console logging and deferred responses

- Add builder.Logging.AddConsole() to DiscordBot Program.cs so logs
  are visible in docker logs.
- Add granular LogInformation/LogError calls to DiscordNewSessionCommand
  and DiscordRescheduleCommand to diagnose failures.
- Use InteractionCallback.DeferredMessage() + ModifyResponseAsync pattern
  for /newsession and /reschedule to avoid Discord 3-second interaction
  timeout.
- Bump version → 3.0.8

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/GmRelay.Web/Components/Layout/NavMenu.razor

@@ -73,7 +73,7 @@
                     </button>
                 </form>
 
-                <div class="nav-version">v3.0.7</div>
+                <div class="nav-version">v3.0.8</div>
             </div>
         </Authorized>
         <NotAuthorized>