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

frontend/src/routes/settings/+page.svelte

@@ -28,6 +28,11 @@
     git_commit_prompt:
       "Generate a concise and professional git commit message based on the following diff and recent history.\\nUse Conventional Commits format (e.g., feat: ..., fix: ..., docs: ...).\\n\\nRecent History:\\n{history}\\n\\nDiff:\\n{diff}\\n\\nCommit Message:",
   };
+  const DEFAULT_LLM_PROVIDER_BINDINGS = {
+    dashboard_validation: "",
+    documentation: "",
+    git_commit: "",
+  };
 
   // State
   let activeTab = "environments";
@@ -77,15 +82,50 @@
       providers: [],
       default_provider: "",
       prompts: { ...DEFAULT_LLM_PROMPTS },
+      provider_bindings: { ...DEFAULT_LLM_PROVIDER_BINDINGS },
+      assistant_planner_provider: "",
+      assistant_planner_model: "",
       ...(llm || {}),
     };
     normalized.prompts = {
       ...DEFAULT_LLM_PROMPTS,
       ...(llm?.prompts || {}),
     };
+    normalized.provider_bindings = {
+      ...DEFAULT_LLM_PROVIDER_BINDINGS,
+      ...(llm?.provider_bindings || {}),
+    };
+    normalized.assistant_planner_provider = llm?.assistant_planner_provider || "";
+    normalized.assistant_planner_model = llm?.assistant_planner_model || "";
     return normalized;
   }
 
+  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 getProviderById(providerId) {
+    if (!providerId) return null;
+    return (settings?.llm_providers || []).find((p) => p.id === providerId) || null;
+  }
+
+  function isDashboardValidationBindingValid() {
+    const providerId = settings?.llm?.provider_bindings?.dashboard_validation;
+    if (!providerId) return true;
+    const provider = getProviderById(providerId);
+    return provider ? isMultimodalModel(provider.default_model) : true;
+  }
+
   // Handle tab change
   function handleTabChange(tab) {
     activeTab = tab;
@@ -670,6 +710,121 @@
             onSave={loadSettings}
           />
 
+          <div class="mt-6 rounded-lg border border-gray-200 bg-white p-4">
+            <h3 class="text-base font-semibold text-gray-900">
+              {$t.settings?.llm_chatbot_settings_title || "Chatbot Planner Settings"}
+            </h3>
+            <p class="mt-1 text-sm text-gray-600">
+              {$t.settings?.llm_chatbot_settings_description ||
+                "Select provider and optional model override for assistant intent planning."}
+            </p>
+
+            <div class="mt-4 grid grid-cols-1 gap-4 md:grid-cols-2">
+              <div>
+                <label for="planner-provider" class="block text-sm font-medium text-gray-700">
+                  {$t.settings?.llm_chatbot_provider || "Chatbot Provider"}
+                </label>
+                <select
+                  id="planner-provider"
+                  bind:value={settings.llm.assistant_planner_provider}
+                  class="mt-1 block w-full rounded-md border border-gray-300 p-2 text-sm"
+                >
+                  <option value="">{$t.dashboard?.use_default || "Use Default"}</option>
+                  {#each settings.llm_providers || [] as provider}
+                    <option value={provider.id}>
+                      {provider.name} ({provider.default_model})
+                    </option>
+                  {/each}
+                </select>
+              </div>
+
+              <div>
+                <label for="planner-model" class="block text-sm font-medium text-gray-700">
+                  {$t.settings?.llm_chatbot_model || "Chatbot Model Override"}
+                </label>
+                <input
+                  id="planner-model"
+                  type="text"
+                  bind:value={settings.llm.assistant_planner_model}
+                  placeholder={$t.settings?.llm_chatbot_model_placeholder || "Optional, e.g. gpt-4.1-mini"}
+                  class="mt-1 block w-full rounded-md border border-gray-300 p-2 text-sm"
+                />
+              </div>
+            </div>
+          </div>
+
+          <div class="mt-6 rounded-lg border border-gray-200 bg-white p-4">
+            <h3 class="text-base font-semibold text-gray-900">
+              {$t.settings?.llm_provider_bindings_title || "Provider Bindings by Task"}
+            </h3>
+            <p class="mt-1 text-sm text-gray-600">
+              {$t.settings?.llm_provider_bindings_description ||
+                "Select which provider is used by default for each LLM task."}
+            </p>
+
+            <div class="mt-4 grid grid-cols-1 gap-4 md:grid-cols-2">
+              <div>
+                <label for="binding-dashboard-validation" class="block text-sm font-medium text-gray-700">
+                  {$t.settings?.llm_binding_dashboard_validation || "Dashboard Validation Provider"}
+                </label>
+                <select
+                  id="binding-dashboard-validation"
+                  bind:value={settings.llm.provider_bindings.dashboard_validation}
+                  class="mt-1 block w-full rounded-md border border-gray-300 p-2 text-sm"
+                >
+                  <option value="">{$t.dashboard?.use_default || "Use Default"}</option>
+                  {#each settings.llm_providers || [] as provider}
+                    <option value={provider.id}>
+                      {provider.name} ({provider.default_model})
+                    </option>
+                  {/each}
+                </select>
+                {#if !isDashboardValidationBindingValid()}
+                  <p class="mt-1 text-xs text-amber-700">
+                    {$t.settings?.llm_multimodal_warning ||
+                      "Dashboard validation requires a multimodal model (image input)."}
+                  </p>
+                {/if}
+              </div>
+
+              <div>
+                <label for="binding-documentation" class="block text-sm font-medium text-gray-700">
+                  {$t.settings?.llm_binding_documentation || "Documentation Provider"}
+                </label>
+                <select
+                  id="binding-documentation"
+                  bind:value={settings.llm.provider_bindings.documentation}
+                  class="mt-1 block w-full rounded-md border border-gray-300 p-2 text-sm"
+                >
+                  <option value="">{$t.dashboard?.use_default || "Use Default"}</option>
+                  {#each settings.llm_providers || [] as provider}
+                    <option value={provider.id}>
+                      {provider.name} ({provider.default_model})
+                    </option>
+                  {/each}
+                </select>
+              </div>
+
+              <div class="md:col-span-2">
+                <label for="binding-git-commit" class="block text-sm font-medium text-gray-700">
+                  {$t.settings?.llm_binding_git_commit || "Git Commit Provider"}
+                </label>
+                <select
+                  id="binding-git-commit"
+                  bind:value={settings.llm.provider_bindings.git_commit}
+                  class="mt-1 block w-full rounded-md border border-gray-300 p-2 text-sm"
+                >
+                  <option value="">{$t.dashboard?.use_default || "Use Default"}</option>
+                  {#each settings.llm_providers || [] as provider}
+                    <option value={provider.id}>
+                      {provider.name} ({provider.default_model})
+                    </option>
+                  {/each}
+                </select>
+              </div>
+            </div>
+          </div>
+
           <div class="mt-6 rounded-lg border border-gray-200 bg-gray-50 p-4">
             <h3 class="text-base font-semibold text-gray-900">
               {$t.settings?.llm_prompts_title || "LLM Prompt Templates"}