fix(web): resolve TDZ error on profile page from shadowed signal var

The profile page failed to render with "Cannot access 'h' before
initialization". The /profile/me branch destructured `signal` from
params and used it in the apiGet call, but later redeclared
`const signal = ac.signal` in the same block scope. Block-scoped const
hoisting put the earlier reference in the temporal dead zone.

Drop the redundant inner declaration and pass `ac.signal` directly to
the form submit listener.

Fixes #233

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/meshcore_hub/web/static/js/spa/pages/profile.js

@@ -167,7 +167,6 @@ ${flashHtml}
 </div>`, container);
 
         const ac = new AbortController();
-        const signal = ac.signal;
 
         container.querySelector('#profile-form').addEventListener('submit', async (e) => {
             e.preventDefault();
@@ -184,7 +183,7 @@ ${flashHtml}
             } catch (err) {
                 router.navigate('/profile?error=' + encodeURIComponent(err.message), true);
             }
-        }, { signal });
+        }, { signal: ac.signal });
 
         return () => ac.abort();