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/globals/Navigation.ts

@@ -3,13 +3,35 @@ import type { GlobalConfig } from "payload";
 export const Navigation: GlobalConfig = {
   slug: "navigation",
   access: { read: () => true },
+  admin: { group: "Site" },
   fields: [
     {
-      name: "primaryLinks",
+      name: "primary",
       type: "array",
       fields: [
         { name: "label", type: "text", required: true },
         { name: "href", type: "text", required: true },
+        { name: "external", type: "checkbox", defaultValue: false },
+      ],
+    },
+    {
+      name: "socials",
+      type: "array",
+      fields: [
+        {
+          name: "platform",
+          type: "select",
+          required: true,
+          options: [
+            { label: "GitHub", value: "github" },
+            { label: "LinkedIn", value: "linkedin" },
+            { label: "Twitter", value: "twitter" },
+            { label: "Mastodon", value: "mastodon" },
+            { label: "RSS", value: "rss" },
+          ],
+        },
+        { name: "label", type: "text" },
+        { name: "href", type: "text", required: true },
       ],
     },
     {