Fix: Ubercoin balance display and refresh issues

- Profile page: Add cache: 'no-store' to always fetch fresh balance data
- Profile page: Update balance immediately after tip using transaction result
  to avoid race conditions where DB hasn't committed yet
- Profile page: Reload profile after 500ms delay for data consistency
- UbercoinTipModal: Clarify "Your balance" to avoid confusion with recipient's

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/lib/components/UbercoinTipModal.svelte

@@ -407,7 +407,7 @@
 
             <div class="balance-row">
                 <span class="coin-icon">Ü</span>
-                <span>Balance: <strong>{formatUbercoin($ubercoinBalance)}</strong></span>
+                <span>Your balance: <strong>{formatUbercoin($ubercoinBalance)}</strong></span>
             </div>
 
             <div class="input-group">