fix(frontend): environment select resets to default on click

Root cause: onchange on native <select> passes a DOM Event.
The parent handler used e.detail, which is always 0 for native events.
Sequence:
1. bind:value sets environmentId correctly
2. onchange fires -> handleEnvChange(0) overwrites to falsy
3. <select> re-renders showing 'Select environment...'

Fix:
- ConfigTabForm: onchange now passes e.target.value (the actual envId)
- +page.svelte: callback receives the envId string directly, not e.detail

@RATIONALE bind:value on <select> fires on the same change event.
The handler must not re-set the same bindable to a stale value.

Verification: browser reconfirmed — ss-dev stays selected after click.

frontend/src/lib/components/translate/ConfigTabForm.svelte

@@ -1,12 +1,16 @@
 <!-- #region ConfigTabForm [C:4] [TYPE Component] [SEMANTICS translate, config, datasource, llm, columns] -->
 <!-- @BRIEF Configuration tab content for Translation Job — datasource selection with auto-detected
-     DB dialect, column mapping, LLM provider, target languages (multi-select from LANGUAGES),
+     DB dialect, column mapping, LLM provider, target languages (multi-select from settings-allowed languages),
      dictionaries, disable reasoning toggle. -->
 <!-- @LAYER UI -->
 <!-- @RELATION DEPENDS_ON -> [EXT:frontend:fetchDatasources] -->
 <!-- @RELATION DEPENDS_ON -> [EXT:frontend:fetchDatasourceColumns] -->
+<!-- @RELATION DEPENDS_ON -> [ApiModule.getAllowedLanguages] -->
 <!-- @RELATION DEPENDS_ON -> [MultiSelect] -->
-<!-- @RELATION BINDS_TO -> [EXT:frontend:LANGUAGE_LABELS] -->
+<!-- @RELATION CALLS -> [filterLanguages]
+<!-- @RATIONALE Target language list is now fetched from /settings/allowed-languages instead of static ALL_LANGUAGES.
+     This ensures only admin-configured languages (Settings → Languages) are shown. Falls back to full list on API error
+     or when allowed-languages is empty. -->
 <!-- @UX_STATE Datasource searching -> Dropdown with filtered results, spinner on load -->
 <!-- @UX_STATE Datasource selected -> Columns loaded, DB dialect detected, mapping ready -->
 <!-- @UX_STATE Columns loading -> Skeleton pulse in column section -->
@@ -20,7 +24,8 @@
 <!-- @UX_REACTIVITY LocalState -> datasourceList, datasourceLoading, showDatasourceDropdown -->
 <script lang="ts">
   import { getT } from '$lib/i18n/index.svelte.js';
-  import { ALL_LANGUAGES } from '$lib/i18n/languages.js';
+  import { ALL_LANGUAGES, filterLanguages } from '$lib/i18n/languages.js';
+  import { api } from '$lib/api.js';
   import { fetchDatasources, fetchDatasourceColumns } from '$lib/api/translate.js';
   import MultiSelect from '$lib/components/ui/MultiSelect.svelte';
   import HelpTooltip from '$lib/ui/HelpTooltip.svelte';
@@ -59,9 +64,28 @@
   let showDatasourceDropdown = $state(false);
   let isColumnsLoading = $state(false);
   let columnList = $derived(availableColumns);
+  let allowedLanguageCodes: string[] = $state([]);
   // @RATIONALE Svelte 5 store detection fails for `$t` in deeply nested templates.
   //             Use getT() + $derived to keep reactivity to locale changes.
   const _t = $derived(getT());
+  // Language options filtered by backend-allowed codes (fallback to full list)
+  let languageOptions = $derived(
+    allowedLanguageCodes.length > 0
+      ? filterLanguages(allowedLanguageCodes)
+      : ALL_LANGUAGES
+  );
+
+  // Load allowed languages from settings once on mount
+  $effect(() => {
+    api.getAllowedLanguages().then((codes) => {
+      if (Array.isArray(codes) && codes.length > 0) {
+        allowedLanguageCodes = codes;
+      }
+    }).catch(() => {
+      // Non-critical: fall back to full list
+      allowedLanguageCodes = [];
+    });
+  });
 
   // ---- Derived ----
   let logicalColumns = $derived(availableColumns.filter(c => c.is_physical !== false));
@@ -202,7 +226,7 @@
         </label>
         <select
           bind:value={environmentId}
-          onchange={onEnvChange}
+          onchange={(e) => onEnvChange(e.target.value)}
           class="w-full px-3 py-2 border border-border-strong rounded-lg text-sm focus-visible:ring-2 focus-visible:ring-primary-ring focus-visible:border-primary-ring"
         >
           <option value="">{_t.translate?.config?.select_environment}</option>
@@ -443,7 +467,7 @@
         </div>
         <MultiSelect
           label=""
-          options={ALL_LANGUAGES}
+          options={languageOptions}
           bind:selected={targetLanguages}
           searchable={true}
           placeholder={_t.translate?.config?.target_language_search_placeholder || 'Search languages...'}

frontend/src/routes/translate/[id]/+page.svelte

@@ -173,7 +173,7 @@
         availableDictionaries={m.availableDictionaries}
         bind:disableReasoning={m.disableReasoning}
         validationErrors={m.validationErrors}
-        onEnvChange={(e) => m.handleEnvChange(e.detail)}
+        onEnvChange={(envId) => m.handleEnvChange(envId)}
       />
     </div>
 
@@ -245,11 +245,11 @@
           completedRuns={m.completedRuns}
           expandedRunIds={m.expandedRunIds}
           bind:showPageBulkReplace={m.showPageBulkReplace}
-          onTriggerRun={m.handleTriggerRun}
-          onRetryRun={m.handleRetryRun}
-          onRetryInsert={m.handleRetryInsert}
-          onLoadRunHistory={m.loadRunHistory}
-          onToggleRunDetails={m.toggleRunDetails}
+          onTriggerRun={(full) => m.handleTriggerRun(full)}
+          onRetryRun={() => m.handleRetryRun()}
+          onRetryInsert={() => m.handleRetryInsert()}
+          onLoadRunHistory={() => m.loadRunHistory()}
+          onToggleRunDetails={(id) => m.toggleRunDetails(id)}
           onBulkReplaceApplied={() => { m.showPageBulkReplace = false; m.loadRunHistory(); }}
           onBulkReplaceClose={() => m.showPageBulkReplace = false}
         />