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>

backend/src/routes/experiments.js

@@ -349,8 +349,14 @@ router.get('/:id/daily-statuses', async (req, res, next) => {
     const exp = await prisma.experiment.findUnique({ where: { id: req.params.id } });
     if (!exp) return res.status(404).json({ error: 'Experiment not found' });
 
+    const where = { animal: { experiment_id: req.params.id } };
+    if (req.query.date) {
+      const d = new Date(req.query.date + 'T00:00:00.000Z');
+      const next = new Date(d); next.setUTCDate(next.getUTCDate() + 1);
+      where.date = { gte: d, lt: next };
+    }
     const statuses = await prisma.dailyStatus.findMany({
-      where: { animal: { experiment_id: req.params.id } },
+      where,
       select: {
         id: true,
         animal_id: true,