v0.4.1: app filtering + clickable dashboard stat cards

Add filter bar (Mind/Futó/Leállítva/Telepíthető) to Alkalmazások page with
URL-based filter persistence. Dashboard stat cards are now clickable links
that navigate to the filtered stacks view.

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

controller/internal/web/templates/dashboard.html

@@ -7,18 +7,18 @@
 </div>
 
 <div class="stats-grid">
-    <div class="stat-card stat-running">
+    <a href="/stacks?filter=running" class="stat-card stat-running">
         <div class="stat-value">{{.RunningCount}}</div>
         <div class="stat-label">Futó alkalmazás</div>
-    </div>
-    <div class="stat-card stat-stopped">
+    </a>
+    <a href="/stacks?filter=stopped" class="stat-card stat-stopped">
         <div class="stat-value">{{.StoppedCount}}</div>
         <div class="stat-label">Leállítva</div>
-    </div>
-    <div class="stat-card stat-total">
+    </a>
+    <a href="/stacks" class="stat-card stat-total">
         <div class="stat-value">{{.TotalCount}}</div>
         <div class="stat-label">Összes alkalmazás</div>
-    </div>
+    </a>
 </div>
 
 {{if .SystemInfo.TotalMemMB}}