feat: landing redesign in resources aesthetic; fix KB search crash

Landing:
- Rebuilt app/(landing)/page.tsx from a 539-line client monolith to a
  ~150-line server component in the /resources editorial style.
- New scoped app/(landing)/landing.css mirrors the resources palette
  (#0c0c0c / lime #d4ff00 / #252525), IBM Plex Mono + Libre
  Baskerville loaded in (landing)/layout.tsx, faint grid overlay.
- Removed the animated Mini* previews and inline Ico* set (clashed
  with the editorial look). Split into components/landing/icons.tsx
  and components/landing/resource-showcase.tsx for separation.
- Resource showcase: one row of six square tiles with the real
  project SVG logos linking to atlas/space-after-dark/proposal-duel/
  zine/learner/governance. Responsive 6 -> 3 -> 2.
- BrandMark accepts an optional style prop.

Fix:
- KB search crashed the Ops page. filteredLeads referenced
  l.member_name (the column is lead_handle), so undefined.toLowerCase()
  threw on every keystroke since the filter memos recompute on shared
  search state across tabs. All Ops filter predicates are now
  null-safe via a shared has() helper; filteredSecrets no longer
  assumes a non-null title.

Docs:
- docs/PERMISSIONS_DESIGN.md: concrete plan for customizable
  permissions, per-item Ops ACLs, and area-lead roles. That work is
  security-sensitive (RLS rewrites on secrets/knowledge_base) and is
  scoped as its own next pass, not bundled here.

266/266 tests pass. Production build clean. No migration this pass.

components/brand-mark.tsx

@@ -1,10 +1,13 @@
+import type { CSSProperties } from 'react'
+
 // The hackerspace.sh brand mark: a minimal terminal prompt glyph (a chevron
 // and an underscore). Inherits the surrounding text color via currentColor,
-// so it picks up the lime accent wherever it sits on the dark sidebar.
-export function BrandMark({ className }: { className?: string }) {
+// or set an explicit color via `style`.
+export function BrandMark({ className, style }: { className?: string; style?: CSSProperties }) {
   return (
     <svg
       className={className}
+      style={style}
       viewBox="0 0 24 24"
       fill="none"
       stroke="currentColor"