feat: thèmes rapides gérés par le backend via fichiers CSS

Les thèmes ne sont plus codés en dur dans le JS. Chaque thème est
un fichier CSS dans src-tauri/resources/themes/, embarqué à la
compilation via include_str!. Le backend expose list_themes et
get_theme_css comme commandes Tauri ; le frontend charge et met en
cache le CSS à la demande.

Ajout du thème "Défaut" (basé sur Shell Indigo) avec commentaires
sur chaque règle et rendu complet des tableaux (en-têtes en
majuscules, bordure extérieure, séparateurs verticaux, lignes
alternées) aligné sur MarkdownRender-nodejs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui/css-modal.js

@@ -1,33 +1,10 @@
+import { listThemes, getThemeCss } from '../services/themes.js';
+
 const CSS_TABS = ['general', 'police', 'contenu', 'avance'];
 let activeTab = CSS_TABS[0];
 
 const QUICK_THEME_KEY = 'pena_quick_theme';
-
-const QUICK_THEMES = {
-  dark: `.content { background: #1e1e2e; color: #cdd6f4; }
-.content h1, .content h2, .content h3, .content h4, .content h5, .content h6 { color: #cdd6f4; }
-.content p, .content ul li, .content ol li { color: #cdd6f4; }
-.content a { color: #89b4fa; }
-.content a:visited { color: #cba6f7; }
-.content code { background: #313244; color: #cba6f7; }
-.content pre { background: #313244; }
-.content blockquote { border-color: #6c7086; color: #a6adc8; }
-.content table td, .content table th { color: #cdd6f4; }`,
-
-  sepia: `.content { background: #f4ecd8; }
-.content h1, .content h2, .content h3, .content h4, .content h5, .content h6 { color: #5c4a1e; }
-.content p, .content ul li, .content ol li { color: #5c4a1e; }
-.content a { color: #7a5c2e; }
-.content code { background: #e8d5b0; color: #5c4a1e; }
-.content pre { background: #e8d5b0; }`,
-
-  'large-text': `.content { font-size: 18px; }
-.content p { line-height: 1.8; }`,
-
-  emerald: `.content a:hover { color: #10b981; }
-.content table th { border-bottom-color: #10b981; }
-.content table td { border-bottom-color: rgba(16, 185, 129, 0.25); }`,
-};
+const themeCssCache = new Map();
 
 function cssKey(tab) { return `pena_css_${tab}`; }
 
@@ -47,7 +24,7 @@ function applyCustomCss() {
   }
   const tabCss = CSS_TABS.map(t => loadTabCss(t)).filter(Boolean).join('\n');
   const activeTheme = localStorage.getItem(QUICK_THEME_KEY);
-  const themeCss = activeTheme ? (QUICK_THEMES[activeTheme] ?? '') : '';
+  const themeCss = activeTheme ? (themeCssCache.get(activeTheme) ?? '') : '';
   styleEl.textContent = [tabCss, themeCss].filter(Boolean).join('\n');
 }
 
@@ -58,7 +35,44 @@ function syncThemeBadges() {
   });
 }
 
-export function initCssModal() {
+function buildThemeBadges(themes) {
+  const list = document.getElementById('quick-themes-list');
+  list.innerHTML = '';
+  for (const { id, label } of themes) {
+    const btn = document.createElement('button');
+    btn.className = 'css-modal__theme-badge';
+    btn.dataset.theme = id;
+    btn.textContent = label;
+    btn.addEventListener('click', async () => {
+      const current = localStorage.getItem(QUICK_THEME_KEY);
+      if (current === id) {
+        localStorage.removeItem(QUICK_THEME_KEY);
+      } else {
+        if (!themeCssCache.has(id)) {
+          const css = await getThemeCss(id);
+          if (css) themeCssCache.set(id, css);
+        }
+        localStorage.setItem(QUICK_THEME_KEY, id);
+      }
+      applyCustomCss();
+      syncThemeBadges();
+    });
+    list.appendChild(btn);
+  }
+}
+
+async function preloadActiveThemeCss() {
+  const activeTheme = localStorage.getItem(QUICK_THEME_KEY);
+  if (activeTheme && !themeCssCache.has(activeTheme)) {
+    const css = await getThemeCss(activeTheme);
+    if (css) themeCssCache.set(activeTheme, css);
+  }
+}
+
+export async function initCssModal() {
+  const themes = await listThemes();
+  buildThemeBadges(themes);
+  await preloadActiveThemeCss();
   applyCustomCss();
   syncThemeBadges();
 
@@ -104,15 +118,4 @@ export function initCssModal() {
     applyCustomCss();
     syncThemeBadges();
   });
-
-  document.querySelectorAll('.css-modal__theme-badge').forEach(btn => {
-    btn.addEventListener('click', () => {
-      const theme = btn.dataset.theme;
-      const current = localStorage.getItem(QUICK_THEME_KEY);
-      if (current === theme) localStorage.removeItem(QUICK_THEME_KEY);
-      else localStorage.setItem(QUICK_THEME_KEY, theme);
-      applyCustomCss();
-      syncThemeBadges();
-    });
-  });
 }