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

frontend/src/components/EnvSelector.svelte

@@ -11,6 +11,7 @@
 <script lang="ts">
   // [SECTION: IMPORTS]
   import { onMount, createEventDispatcher } from 'svelte';
+  import { t } from '../lib/i18n';
   // [/SECTION]
 
   // [SECTION: PROPS]
@@ -48,7 +49,7 @@
     value={selectedId}
     on:change={handleSelect}
   >
-    <option value="" disabled>-- Choose an environment --</option>
+    <option value="" disabled>{$t.common?.choose_environment || "-- Choose an environment --"}</option>
     {#each environments as env}
       <option value={env.id}>{env.name} ({env.url})</option>
     {/each}
@@ -57,4 +58,4 @@
 <!-- [/SECTION] -->
 
 
-<!-- [/DEF:EnvSelector:Component] -->
+<!-- [/DEF:EnvSelector:Component] -->