feat: per-app telemetry reset button on app detail page

Adds "Telemetria törlése" button that deletes all telemetry records and
known issues for a specific app. Useful after major app updates when old
data is no longer representative.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hub/internal/web/templates/app_detail.html

@@ -27,9 +27,20 @@
             <a href="?period=30d" class="period-btn{{if eq .Period "30d"}} active{{end}}">30 nap</a>
         </div>
 
+        {{if eq .Flash "telemetry_reset"}}
+        <div class="flash flash-success" style="margin-top: 1rem;">Telemetria sikeresen törölve.</div>
+        {{end}}
+
         <!-- Overview card -->
         <section class="card">
-            <h2>{{if .Summary}}{{if .Summary.DisplayName}}{{.Summary.DisplayName}}{{else}}{{.AppName}}{{end}}{{else}}{{.AppName}}{{end}}</h2>
+            <div style="display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 0.5rem;">
+                <h2 style="margin: 0;">{{if .Summary}}{{if .Summary.DisplayName}}{{.Summary.DisplayName}}{{else}}{{.AppName}}{{end}}{{else}}{{.AppName}}{{end}}</h2>
+                <form method="POST" action="/apps/{{.AppName}}/reset-telemetry{{if .Period}}?period={{.Period}}{{end}}"
+                      onsubmit="return confirm('Biztosan törlöd a(z) {{.AppName}} összes telemetriai adatát? Ez nem vonható vissza.');">
+                    <input type="hidden" name="csrf_token" value="{{.CSRFToken}}">
+                    <button type="submit" class="btn btn-sm btn-danger">Telemetria törlése</button>
+                </form>
+            </div>
             <div class="info-grid">
                 <div class="info-item">
                     <span class="label">App neve</span>