feat(site): port stitch design system + seed-ready content model

Ports the "Technical Editorial" design sample into real TSX wired to
Payload globals/collections. Home/About/Projects (list+detail)/Contact
pages render against Payload data. Expands schemas (Home principles,
About timeline/skills/gear, Contact channels) to cover the full design
surface. Adds seed script that populates realistic AI-drafted content
for first boot. Defers writing/resume routes per scope cut.

- Design tokens: Material-3 palette + Space Grotesk/Inter typography
  scale + dot-grid + glassmorphism utilities
- Shared layout: Nav, Footer, StatusTerminal, GridOverlay, Button,
  TechChip in src/components/site
- Schemas: expand 5 globals + 6 collections; add auto-slug hook
- Seed: scripts/seed.ts — idempotent upsert for media, categories,
  6 projects, 8 gear, 3 posts, 5 globals; generates placeholder admin
- Contact: form + /api/contact route with optional Turnstile verify
- Rename TURNSTILE_SITE_KEY -> NEXT_PUBLIC_TURNSTILE_SITE_KEY (client)
- Remove dead src/components/SiteHeader|SiteFooter|StatusTerminal

src/collections/Categories.ts

@@ -3,19 +3,13 @@ import type { CollectionConfig } from "payload";
 export const Categories: CollectionConfig = {
   slug: "categories",
   access: { read: () => true },
-  admin: { useAsTitle: "name", defaultColumns: ["name", "slug", "accent"] },
+  admin: {
+    useAsTitle: "name",
+    defaultColumns: ["name", "slug"],
+    group: "Content",
+  },
   fields: [
     { name: "name", type: "text", required: true },
     { name: "slug", type: "text", required: true, unique: true, index: true },
-    {
-      name: "accent",
-      type: "select",
-      defaultValue: "primary",
-      options: [
-        { label: "Primary (cyan)", value: "primary" },
-        { label: "Secondary (magenta)", value: "secondary" },
-        { label: "Tertiary (green)", value: "tertiary" },
-      ],
-    },
   ],
 };