perf: server-side caching + remove bulk status fetch from experiment page

- Add backend/src/lib/cache.js — in-process TTL Map cache with
  prefix-based invalidation; no external dependencies

- Cache /experiments/:id/calendar?field=X per (experimentId, field).
  Invalidated immediately on any DailyStatus write.

- Cache /experiments/:id/daily-statuses per (experimentId, date, analysisOnly).
  Invalidated immediately on any DailyStatus write (create/update/delete
  and analysis-summary saves all clear the relevant prefix).

- Add ?analysisOnly=true to /daily-statuses: filters rows where
  analysis_summary IS NOT NULL. Charts are the only consumer and already
  discard rows without analysis data; pre-filtering server-side avoids
  sending the full status payload (71 rows → 1 for this experiment).

- ExperimentCalendar: remove allStatuses prop, fetch calendar data
  directly via API. The component now issues one small GET per field
  selection change instead of the parent loading thousands of rows upfront.

- ExperimentDetail: pass analysisOnly:true to getDailyStatuses;
  drop allStatuses prop from ExperimentCalendar. Cold experiment page
  load no longer fetches every daily status record.

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

backend/src/routes/experiments.js

@@ -1,6 +1,7 @@
 const router = require('express').Router();
 const { body } = require('express-validator');
 const prisma = require('../lib/prisma');
+const cache = require('../lib/cache');
 const auditMiddleware = require('../middleware/auditMiddleware');
 const { validateRequest } = require('../middleware/errorHandler');
 const { v4: uuidv4 } = require('uuid');
@@ -311,10 +312,15 @@ router.put('/:id/subject-template', async (req, res, next) => {
 // Returns { field, days: { "YYYY-MM-DD": count } } where count = subjects with non-empty value that day.
 router.get('/:id/calendar', async (req, res, next) => {
   try {
+    const field = req.query.field ?? '';
+    const cacheKey = `exp:${req.params.id}:cal:${field}`;
+
+    const cached = cache.get(cacheKey);
+    if (cached) return res.json(cached);
+
     const exp = await prisma.experiment.findUnique({ where: { id: req.params.id } });
     if (!exp) return res.status(404).json({ error: 'Experiment not found' });
 
-    const field = req.query.field ?? '';
     const BUILTIN_KEYS_SET = new Set(['experiment_description', 'vitals', 'treatment', 'notes']);
     const isBuiltin = BUILTIN_KEYS_SET.has(field);
 
@@ -339,22 +345,37 @@ router.get('/:id/calendar', async (req, res, next) => {
       }
     }
 
-    res.json({ field, days });
+    const result = { field, days };
+    cache.set(cacheKey, result);
+    res.json(result);
   } catch (err) { next(err); }
 });
 
 // GET /api/experiments/:id/daily-statuses  — all statuses for all subjects, analysis_summary included
+// ?date=YYYY-MM-DD  — filter to a single day
+// ?analysisOnly=true  — only return statuses that have a saved analysis_summary (for charts)
 router.get('/:id/daily-statuses', async (req, res, next) => {
   try {
+    const date         = req.query.date ?? '';
+    const analysisOnly = req.query.analysisOnly === 'true';
+    const cacheKey     = `exp:${req.params.id}:ds:${analysisOnly ? '1' : '0'}:${date}`;
+
+    const cached = cache.get(cacheKey);
+    if (cached) return res.json(cached);
+
     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');
+    if (date) {
+      const d    = new Date(date + 'T00:00:00.000Z');
       const next = new Date(d); next.setUTCDate(next.getUTCDate() + 1);
       where.date = { gte: d, lt: next };
     }
+    if (analysisOnly) {
+      where.NOT = { analysis_summary: null };
+    }
+
     const statuses = await prisma.dailyStatus.findMany({
       where,
       select: {
@@ -370,6 +391,8 @@ router.get('/:id/daily-statuses', async (req, res, next) => {
       },
       orderBy: { date: 'asc' },
     });
+
+    cache.set(cacheKey, statuses);
     res.json(statuses);
   } catch (err) { next(err); }
 });