feat: replace calendar day modal with dedicated day-view page

Calendar day clicks now navigate to /experiments/:id/day/:date
(with ?field= param). ExperimentDayView shows a sticky-column table
of all subjects with data that day, inline edit via modal, and a
session-metrics bar chart from analysis_summary. Subject name links
to /daily-statuses/:id. Backend adds ?date= filtering to
GET /experiments/:id/daily-statuses.

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

frontend/src/App.jsx

@@ -5,6 +5,7 @@ import Dashboard from './pages/Dashboard';
 import ExperimentDetail from './pages/ExperimentDetail';
 import AnimalDetail from './pages/AnimalDetail';
 import DailyStatusDetail from './pages/DailyStatusDetail';
+import ExperimentDayView from './pages/ExperimentDayView';
 
 function Navbar() {
   return (
@@ -57,6 +58,7 @@ export default function App() {
         <Routes>
           <Route path="/" element={<Dashboard />} />
           <Route path="/experiments/:id" element={<ExperimentDetail />} />
+          <Route path="/experiments/:id/day/:date" element={<ExperimentDayView />} />
           <Route path="/animals/:id" element={<AnimalDetail />} />
           <Route path="/daily-statuses/:id" element={<DailyStatusDetail />} />
           <Route path="*" element={<NotFound />} />