feat: add Pomodoro timer for productivity

- Create PomodoroTimer component with 25/5/15 minute intervals
- Support work sessions, short breaks, and long breaks
- Track completed sessions with visual counter
- Add progress bar and audio notification when timer completes
- Auto-advance to appropriate break after work session
- Add pause/resume and reset functionality
- Integrate timer in desktop right column above todos/RSS

src/pages/Index.tsx

@@ -37,6 +37,7 @@ import { downloadNoteAsMarkdown, downloadAllNotesAsMarkdown, downloadTodosAsMark
 import { TemplateSelector } from "@/components/TemplateSelector";
 import type { NoteTemplate } from "@/utils/noteTemplates";
 import { AdvancedSearch, type SearchFilters, type TagOption } from "@/components/AdvancedSearch";
+import { PomodoroTimer } from "@/components/PomodoroTimer";
 
 // ===== FONCTIONS UTILITAIRES TIMEZONE EUROPE/PARIS =====
 
@@ -1740,8 +1741,13 @@ const Index = () => {
             )}
           </div>
 
-          {/* Right Column: Todos & RSS Boxes side by side */}
-          <div className="grid grid-cols-2 gap-6">
+          {/* Right Column: Pomodoro Timer, Todos & RSS */}
+          <div className="space-y-6">
+            {/* Pomodoro Timer */}
+            <PomodoroTimer />
+
+            {/* Todos & RSS Boxes side by side */}
+            <div className="grid grid-cols-2 gap-6">
             {/* Todos Box */}
             <Card className="shadow-lg">
               <CardHeader className="pb-3">
@@ -1971,6 +1977,7 @@ const Index = () => {
             </Card>
 
           </div>
+          </div>
         </div>
       </div>