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

frontend/src/routes/migration/mappings/+page.svelte

@@ -106,7 +106,7 @@
       });
 
       mappings = [...mappings.filter(m => m.source_db_uuid !== sourceUuid), savedMapping];
-      success = "Mapping saved successfully";
+      success = $t.migration?.mapping_saved || "Mapping saved successfully";
     } catch (e) {
       error = e.message;
     }
@@ -116,20 +116,20 @@
 
 <!-- [SECTION: TEMPLATE] -->
 <div class="max-w-6xl mx-auto p-6">
-  <PageHeader title="Database Mapping Management" />
+  <PageHeader title={$t.migration?.mapping_management || "Database Mapping Management"} />
 
   {#if loading}
-    <p>Loading environments...</p>
+    <p>{$t.migration?.loading_envs || "Loading environments..."}</p>
   {:else}
     <div class="grid grid-cols-1 md:grid-cols-2 gap-6 mb-8">
       <EnvSelector
-        label="Source Environment"
+        label={$t.migration?.source_env || "Source Environment"}
         bind:selectedId={sourceEnvId}
         {environments}
         on:change={() => { sourceDatabases = []; mappings = []; suggestions = []; }}
       />
       <EnvSelector
-        label="Target Environment"
+        label={$t.migration?.target_env || "Target Environment"}
         bind:selectedId={targetEnvId}
         {environments}
         on:change={() => { targetDatabases = []; mappings = []; suggestions = []; }}
@@ -142,7 +142,7 @@
         disabled={!sourceEnvId || !targetEnvId || sourceEnvId === targetEnvId || fetchingDbs}
         isLoading={fetchingDbs}
       >
-        Fetch Databases & Suggestions
+        {$t.migration?.fetch_dbs || "Fetch Databases & Suggestions"}
       </Button>
     </div>
 
@@ -167,7 +167,7 @@
         on:update={handleUpdate}
       />
     {:else if !fetchingDbs && sourceEnvId && targetEnvId}
-      <p class="text-gray-500 italic">Select environments and click "Fetch Databases" to start mapping.</p>
+      <p class="text-gray-500 italic">{$t.migration?.mapping_hint || 'Select environments and click "Fetch Databases" to start mapping.'}</p>
     {/if}
   {/if}
 </div>