refactor(dashboard): compose the page from a tile registry

The dashboard page held every tile and chart card in one 2,100-line
function: a 1,279-line inline block pushed 24 cards behind 36 show flags.
The cards now live in components/dashboard/tiles/, each with its layout
widget, its own visibility rule (data floor, module, resolved layout) and
its render; the layout toggle and order are applied once by the registry.

- use-dashboard-data: the snapshot or legacy reads, the layout, mood,
  thresholds, the batched chart series and the loading gate
- tile-context: summaries, display units, comparison deltas, freshness,
  directions and target bands, derived once per render
- strip-tiles / chart-tiles: the two registries and their builders
- dashboard-tiles: the strip, the chart row, their skeletons and the
  empty state

The page is a composer of about 170 lines. Rendering is unchanged. The
guards that read page-client.tsx read the whole registry through one
helper; the weight-direction, HRV freshness, BP-in-target comparison and
chart-reveal checks now build the real tiles instead of matching text.

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": 410,
-  "total": 147795,
+  "count": 408,
+  "total": 144385,
   "entries": {
     "app/achievements/page.tsx :: AchievementsPage": 206,
     "app/api/admin/backups/upload/route.ts :: apiHandler(arg)": 314,
@@ -76,8 +76,6 @@
     "app/labs/page.tsx :: LabsPage": 228,
     "app/medications/page-client.tsx :: MedicationsPageClient": 590,
     "app/notifications/page.tsx :: NotificationsPage": 327,
-    "app/page-client.tsx :: DashboardPageClient": 2131,
-    "app/page-client.tsx :: DashboardPageClient > (anonymous)": 1279,
     "components/activity/activity-calendar-card.tsx :: ActivityCalendarCard": 470,
     "components/admin/admin-shell.tsx :: AdminShell": 254,
     "components/admin/api-token-overview-section.tsx :: ApiTokenOverviewSection": 212,