feat(web): SessionPage — rehearsal date detail view

Shows date, optional label/notes (admin-editable), and a flat list
of all recordings from that session. Each recording links to SongPage
and shows tags, key, BPM chips inline.

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

web/src/App.tsx

@@ -5,6 +5,7 @@ import { ThemeProvider, useTheme } from "./theme";
 import { LoginPage } from "./pages/LoginPage";
 import { HomePage } from "./pages/HomePage";
 import { BandPage } from "./pages/BandPage";
+import { SessionPage } from "./pages/SessionPage";
 import { SongPage } from "./pages/SongPage";
 import { SettingsPage } from "./pages/SettingsPage";
 import { InvitePage } from "./pages/InvitePage";
@@ -63,6 +64,14 @@ export default function App() {
                 </PrivateRoute>
               }
             />
+            <Route
+              path="/bands/:bandId/sessions/:sessionId"
+              element={
+                <PrivateRoute>
+                  <SessionPage />
+                </PrivateRoute>
+              }
+            />
             <Route
               path="/bands/:bandId/songs/:songId"
               element={