feat: support multi-format — images, CSV, JSON, TXT + fix PDF embed

- PDF: <iframe> → <embed> (plus compatible webview Tauri)
- Images: .png .jpg .gif .svg .webp .bmp .ico → rendu standalone avec toolbar
- CSV: rendu en tableau HTML avec headers sticky
- JSON: affichage formaté avec indentation (html.escape)
- Texte: .txt .log .yml .yaml .py .js .sh .toml .ini → <pre> mono
- CSS: .image-viewer-body, .csv-table, .text-viewer, .json-viewer, .file-toolbar

frontend/js/viewer.js

@@ -431,13 +431,78 @@ export function renderFile(data) {
         </div>
         <div class="pdf-body">
           ${tocHtml}
-          <iframe src="${pdfUrl}" class="pdf-iframe" title="${escapeHtml(data.title)}"></iframe>
+          <embed src="${pdfUrl}" class="pdf-iframe" type="application/pdf" title="${escapeHtml(data.title)}"></embed>
         </div>
       </div>`;
     lucide.createIcons();
     return;
   }
 
+  // Handle images
+  if (data.is_image) {
+    const imgUrl = `/api/file/${encodeURIComponent(data.vault)}/raw?path=${encodeURIComponent(data.path)}`;
+    area.innerHTML = `
+      <div class="image-viewer-container">
+        <div class="file-toolbar">
+          <span class="file-info">${escapeHtml(data.title)}</span>
+          <button class="btn-action" onclick="window.open('${imgUrl}', '_blank')">
+            <i data-lucide="maximize" style="width:14px;height:14px"></i> Plein écran
+          </button>
+          <button class="btn-action" onclick="window.open('/api/file/${encodeURIComponent(data.vault)}/download?path=${encodeURIComponent(data.path)}', '_blank')">
+            <i data-lucide="download" style="width:14px;height:14px"></i> Télécharger
+          </button>
+        </div>
+        <div class="image-viewer-body">
+          ${data.html}
+        </div>
+      </div>`;
+    lucide.createIcons();
+    return;
+  }
+
+  // Handle CSV
+  if (data.is_csv) {
+    area.innerHTML = `
+      <div class="text-viewer-container">
+        <div class="file-toolbar">
+          <span class="file-info">CSV — ${escapeHtml(data.title)}</span>
+          <button class="btn-action" onclick="window.open('/api/file/${encodeURIComponent(data.vault)}/download?path=${encodeURIComponent(data.path)}', '_blank')">
+            <i data-lucide="download" style="width:14px;height:14px"></i> Télécharger
+          </button>
+        </div>
+        <div class="text-viewer-body">${data.html}</div>
+      </div>`;
+    lucide.createIcons();
+    return;
+  }
+
+  // Handle JSON and plain text
+  if (data.is_json || data.extension === '.txt' || data.extension === '.log' || data.extension === '.yml' || data.extension === '.yaml' || data.extension === '.sh' || data.extension === '.py' || data.extension === '.js' || data.extension === '.toml' || data.extension === '.ini' || data.extension === '.cfg' || data.extension === '.conf' || data.extension === '.env') {
+    // Read raw content for plain text
+    fetch(`/api/file/${encodeURIComponent(data.vault)}/raw?path=${encodeURIComponent(data.path)}`)
+      .then(r => r.text())
+      .then(text => {
+        const extClass = `lang-${data.extension.replace('.', '')}`;
+        area.innerHTML = `
+          <div class="text-viewer-container">
+            <div class="file-toolbar">
+              <span class="file-info">${escapeHtml(data.title)}</span>
+              <button class="btn-action" onclick="window.open('/api/file/${encodeURIComponent(data.vault)}/download?path=${encodeURIComponent(data.path)}', '_blank')">
+                <i data-lucide="download" style="width:14px;height:14px"></i> Télécharger
+              </button>
+            </div>
+            <div class="text-viewer-body">
+              <pre class="${extClass}"><code>${escapeHtml(text)}</code></pre>
+            </div>
+          </div>`;
+        lucide.createIcons();
+      })
+      .catch(() => {
+        area.innerHTML = `<p class="error">Erreur lors du chargement du fichier.</p>`;
+      });
+    return;
+  }
+
   // Handle unsupported (binary) files
   if (data.unsupported) {
     const sizeStr = data.size_bytes