feat: Admin Insights page — charts for signups, recipes, tiers, usage (v0.55.0)

New Admin > Insights: signups/day and recipes-created/day (manual vs AI)
over the last 30 days, users by tier, recipes by visibility, monthly AI
call totals (6 months), and support tickets by status.

Two hand-rolled SVG chart components (bar-chart.tsx, time-series-chart.tsx)
instead of pulling in a charting library — avoids a new dependency and
any React 19 peer-dep risk. Both ship a hover tooltip (crosshair for the
time series, per-bar for the bar chart) and a "show as table" toggle per
the dataviz method's accessibility requirement.

Repurposed the app's existing (previously unused, grayscale-only)
shadcn --chart-1..5 CSS variables with a validated categorical palette —
run through the dataviz skill's CVD/contrast validator for both light and
dark surfaces (both pass; three light-mode slots fall under 3:1 contrast
by design, mitigated by the charts' direct value/axis labels).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "epicure",
-  "version": "0.54.1",
+  "version": "0.55.0",
   "private": true,
   "scripts": {
     "dev": "pnpm --filter web dev",