fix(charts): round y ticks, calendar x ticks and labels beside the plot

The value chart's axes and labels, as drawn on a 90-day blood pressure
view on a tablet:

- Y ticks were whatever Recharts split the padded domain into, so the
  labels read 57, 83, 109. The domain is now widened to a 1/2/5 step
  and every tick is handed to the axis, evenly spaced and all drawn.
- X ticks were every n-th point, so their dates drifted with the data.
  They now fall on a calendar grid (days, Mondays, two weeks, months,
  quarters, years), each on the point nearest the grid line, and the
  step is the smallest whose labels fit the measured plot width.
- The "your average" label sat inside the plot over the readings, and a
  target zone's label was clipped to its first letter. Both now sit
  beside the plot, in a right margin sized to the longest label.

A browser test draws the axes with Recharts and pins the tick values,
the Monday grid, and both labels outside the plot clear of every dot.

src/__tests__/baselines/source-function-lines.json

@@ -1,7 +1,7 @@
 {
   "$comment": "Production functions over 200 lines, keyed \"file :: name\", and their length. Maintained by src/__tests__/source-size-ratchet.test.ts.",
   "count": 355,
-  "total": 114773,
+  "total": 114755,
   "entries": {
     "app/achievements/page.tsx :: AchievementsPage": 206,
     "app/api/admin/backups/upload/route.ts :: apiHandler(arg)": 314,
@@ -70,7 +70,7 @@
     "components/auth/claim-profile.tsx :: ClaimProfile": 429,
     "components/auth/mfa-login-step.tsx :: MfaLoginStep": 217,
     "components/charts/compliance-heatmap.tsx :: ComplianceHeatmap": 325,
-    "components/charts/health-chart.tsx :: HealthChart": 488,
+    "components/charts/health-chart.tsx :: HealthChart": 470,
     "components/charts/medication-compliance-chart.tsx :: MedicationComplianceChart": 543,
     "components/charts/mood-chart.tsx :: MoodChart": 896,
     "components/charts/mood-heatmap.tsx :: MoodHeatmap": 296,