Multi-Modell + Vision: OpenRouter (GLM 5.3 Flash), Bild-Upload, Tour-Feature, Dashboard-Fixes

- Modell-Registry (DeepSeek direkt + OpenRouter z-ai/glm-5.3-flash), Modellwahl pro Session, Reasoning-Effort max (env-konfigurierbar)
- Bild-Upload für Vision-Modelle (User) + Agent-screenshot()-Tool (nur Vision)
- Tour-Planung: geocode + save_tour mit GPX-Export und Karten-Sektion
- Fix: System-Prompt wird jetzt wirklich an die API gesendet, inkl. aktuellem Dashboard-Dateinamen für Folge-Updates
- Fix: History-Sanitizer gegen 400-Fehler (nie mitten in Tool-Gruppen kürzen)
- Fix: reasoning_content-Roundtrip (Pflicht bei DeepSeek mit tools)
- Fix: Dashboards ohne Browser-Cache ausliefern

public/index.html

@@ -27,9 +27,14 @@
       <button id="logoutBtn" class="text-sm text-slate-400 hover:text-red-400" title="Abmelden">⎋</button>
     </div>
     <button id="newSessionBtn"
-            class="m-4 py-2 rounded-lg bg-blue-600 hover:bg-blue-700 text-white font-semibold text-sm">
+            class="m-4 mb-2 py-2 rounded-lg bg-blue-600 hover:bg-blue-700 text-white font-semibold text-sm">
       + Neue Recherche
     </button>
+    <div class="mx-4 mb-2">
+      <label class="text-xs text-slate-400 block mb-1" for="modelSelectDesktop">Modell</label>
+      <select id="modelSelectDesktop"
+              class="w-full px-2 py-1.5 rounded-lg border text-sm dark:bg-slate-800 dark:border-slate-700 border-slate-300 focus:outline-none focus:ring-2 focus:ring-blue-500"></select>
+    </div>
     <div id="sessionList" class="flex-1 overflow-y-auto px-2 space-y-1"></div>
     <div class="p-3 text-xs text-slate-400 border-t dark:border-slate-800 border-slate-200">
       <div id="userName" class="font-medium text-slate-500 dark:text-slate-400 mb-1"></div>
@@ -43,6 +48,8 @@
     <div class="md:hidden flex items-center gap-2 p-3 border-b dark:border-slate-800 border-slate-200 bg-white dark:bg-slate-900">
       <button id="menuBtn" class="px-2 py-1 rounded bg-slate-200 dark:bg-slate-800">☰</button>
       <span class="font-bold truncate flex-1" id="mobileTitle">Research Agent</span>
+      <select id="modelSelectMobile"
+              class="px-2 py-1 rounded-lg border text-xs dark:bg-slate-800 dark:border-slate-700 border-slate-300 focus:outline-none"></select>
     </div>
 
     <!-- Activity bar -->
@@ -69,7 +76,15 @@
 
     <!-- Input -->
     <div class="p-4 border-t dark:border-slate-800 border-slate-200 bg-white dark:bg-slate-900">
+      <div id="imagePreview" class="hidden mb-2 relative">
+        <img id="imagePreviewImg" src="" alt="Vorschau" class="max-h-40 rounded-xl border dark:border-slate-700 border-slate-300">
+        <button id="imageRemoveBtn" type="button" title="Bild entfernen"
+                class="absolute -top-2 -left-2 w-6 h-6 rounded-full bg-red-600 text-white text-xs font-bold">✕</button>
+      </div>
       <form id="chatForm" class="flex gap-2 items-end">
+        <input type="file" id="imageInput" accept="image/jpeg,image/png,image/webp" class="hidden">
+        <button id="imageBtn" type="button" title="Bild anhängen (nur Vision-Modelle)"
+                class="px-3 py-2.5 rounded-xl border dark:border-slate-700 border-slate-300 dark:bg-slate-800 hover:dark:bg-slate-700 text-lg leading-none">📷</button>
         <textarea id="input" rows="1" placeholder="Thema eingeben… z.B. „Beste Self-Hosted Social-Media-Alternativen 2026“"
                   class="flex-1 resize-none px-3 py-2.5 rounded-xl border dark:bg-slate-800 dark:border-slate-700 border-slate-300 focus:outline-none focus:ring-2 focus:ring-blue-500 max-h-40"></textarea>
         <button id="sendBtn" type="submit"