feat: add debug page with tables and logs viewer (Step 1)

Backend:
- Add /debug/tables endpoint to dump SQLite tables
- Add /debug/logs endpoint to read scrap.log

Frontend:
- Add react-router-dom for navigation
- Create HomePage and DebugPage components
- Add navigation bar with Debug link
- Style debug page with Gruvbox theme
- Fix package.json dependencies versions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/App.jsx

@@ -1,21 +1,39 @@
 import React from "react";
+import { BrowserRouter, Routes, Route, NavLink } from "react-router-dom";
+import HomePage from "./pages/HomePage";
+import DebugPage from "./pages/DebugPage";
 
 const App = () => (
-  <div className="app-shell">
-    <header className="app-header">
-      <div className="brand">suivi_produits</div>
-      <div className="actions">
-        <button className="btn">Add Product</button>
-        <button className="btn">Refresh</button>
-      </div>
-    </header>
-    <main className="app-grid">
-      {/* état vide avant ajout de produit */}
-      <section className="empty-state">
-        <p>Aucun produit pour l'instant, ajoutez un lien Amazon.fr !</p>
-      </section>
-    </main>
-  </div>
+  <BrowserRouter>
+    <div className="app-shell">
+      <header className="app-header">
+        <div className="brand">
+          <NavLink to="/">suivi_produits</NavLink>
+        </div>
+        <nav className="nav-links">
+          <NavLink to="/" className={({ isActive }) => isActive ? "active" : ""}>
+            <i className="fa-solid fa-home"></i> Accueil
+          </NavLink>
+          <NavLink to="/debug" className={({ isActive }) => isActive ? "active" : ""}>
+            <i className="fa-solid fa-bug"></i> Debug
+          </NavLink>
+        </nav>
+        <div className="actions">
+          <button className="btn btn-primary">
+            <i className="fa-solid fa-plus"></i> Add Product
+          </button>
+          <button className="btn">
+            <i className="fa-solid fa-refresh"></i> Refresh
+          </button>
+        </div>
+      </header>
+
+      <Routes>
+        <Route path="/" element={<HomePage />} />
+        <Route path="/debug" element={<DebugPage />} />
+      </Routes>
+    </div>
+  </BrowserRouter>
 );
 
 export default App;