feat(assistant): add multi-dialog UX, task-aware llm settings, and i18n cleanup

frontend/src/components/llm/ProviderConfig.svelte

@@ -29,6 +29,20 @@
   let testStatus = { type: "", message: "" };
   let isTesting = false;
 
+  function isMultimodalModel(modelName) {
+    const token = (modelName || "").toLowerCase();
+    if (!token) return false;
+    return (
+      token.includes("gpt-4o") ||
+      token.includes("gpt-4.1") ||
+      token.includes("vision") ||
+      token.includes("vl") ||
+      token.includes("gemini") ||
+      token.includes("claude-3") ||
+      token.includes("claude-sonnet-4")
+    );
+  }
+
   function resetForm() {
     formData = {
       name: "",
@@ -295,6 +309,13 @@
             >
               {provider.is_active ? $t.llm.active : "Inactive"}
             </span>
+            <span
+              class={`text-xs px-2 py-0.5 rounded-full ${isMultimodalModel(provider.default_model) ? "bg-sky-100 text-sky-800" : "bg-amber-100 text-amber-800"}`}
+            >
+              {isMultimodalModel(provider.default_model)
+                ? ($t.llm?.multimodal || "Multimodal")
+                : ($t.llm?.text_only || "Text only")}
+            </span>
           </div>
           <div class="text-sm text-gray-500">
             {provider.provider_type} • {provider.default_model}