feat: complete i18n coverage — all dynamic content translated

All remaining French strings converted to t() calls:
- ui.js: create/delete file/dir modals, rename/copy/bookmark toasts
- palette.js: confirm dialogs, error toasts
- search.js: result summary text with interpolation
- config.js: about/diagnostics section labels
- auth.js: admin panel title
- viewer.js: forge popout labels
- dashboard.js: shared widget buttons, date locale-aware

57 new locale keys for dynamic content (modals, toasts, admin, about)
Total: 597 keys per language

All 26 modules validated — 163 exports, 0 errors

frontend/js/viewer.js

@@ -10,6 +10,7 @@ import { renderMermaidBlocks } from './mermaid-viewer.js';
 import { DashboardStatsWidget, DashboardRecentWidget, DashboardBookmarkWidget, DashboardSharedWidget, DashboardConflictsWidget } from './dashboard.js';
 import { openShareDialog } from './config.js';
 import { cacheViewedFile, getCachedFile } from './offline.js';
+import { t } from './i18n.js';
 // ---------------------------------------------------------------------------
 // Outline/TOC Manager
 // ---------------------------------------------------------------------------
@@ -534,7 +535,7 @@ export function renderFile(data) {
     var titleInp = document.getElementById("editor-title-input");
     var fileInp = document.getElementById("editor-filename-input");
     if (brand) brand.textContent = "Forge";
-    if (titleInp) { titleInp.value = data.title || ''; titleInp.placeholder = 'Titre...'; }
+    if (titleInp) { titleInp.value = data.title || ''; titleInp.placeholder = t('forge.title_placeholder'); }
     if (fileInp) fileInp.value = data.path.split('/').pop();
     bodyEl.innerHTML = "";
     bodyEl.style.overflow = "hidden";
@@ -547,7 +548,7 @@ export function renderFile(data) {
     safeCreateIcons();
   });
 
-  const openNewWindowBtn = el("button", { class: "btn-action", title: "Ouvrir dans une nouvelle fenetre" }, [icon("external-link", 14), document.createTextNode("pop-out")]);
+  const openNewWindowBtn = el("button", { class: "btn-action", title: t("forge.popout") }, [icon("external-link", 14), document.createTextNode(t("forge.popout_label"))]);
   openNewWindowBtn.addEventListener("click", () => {
     const popoutUrl = `/popout/${encodeURIComponent(data.vault)}/${encodeURIComponent(data.path)}`;
     window.open(popoutUrl, `popout_${data.vault}_${data.path.replace(/[^a-zA-Z0-9]/g, "_")}`, "width=1000,height=700,menubar=no,toolbar=no,location=no,status=no,resizable=yes,scrollbars=no");