Major product upgrade: landing page, scanning UI, admin panel, working reports

Frontend:
- New public marketing landing page at / (hero, features, stats, how-it-works, CTA)
- New /scans page surfacing the scanning engine: asset health grid, one-click
  full scan, live scanner findings feed, 24h stats
- New /admin panel (was a 404 from the sidebar): audit report generation and
  instant PDF snapshot download
- Reports page: now visible to all roles, working PDF downloads, posture
  snapshot export for IT/admin
- Findings page: full-text search, sorting (severity/newest/title), severity
  count chips, CSV export
- Dashboard: scan activity strip, Run Scan + Export PDF quick actions
- Footprint page: summary stat cards
- api.ts: scanning, reports, and PDF download endpoints + types;
  fixed missing resolution_note on Finding type
- Removed unsupported eslint key from next.config.ts

Backend:
- Audit reports: list/get/PDF now open to executives and IT admins with strict
  tenant isolation (was trustos_admin-only, leaving tenants unable to see
  their own reports); PDF snapshot open to IT admins; generation stays
  admin-only

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

frontend/src/components/Sidebar.tsx

@@ -3,12 +3,13 @@ import Link from "next/link";
 import { usePathname } from "next/navigation";
 import { useAuth } from "@/hooks/useAuth";
 import {
-  LayoutDashboard, Shield, Search, FileText, Settings, LogOut, ChevronRight
+  LayoutDashboard, Shield, Search, FileText, Settings, LogOut, Radar
 } from "lucide-react";
 
 const NAV = [
   { href: "/dashboard", icon: LayoutDashboard, label: "Vault Dashboard" },
   { href: "/findings", icon: Shield, label: "Findings" },
+  { href: "/scans", icon: Radar, label: "Scanning", roles: ["it_admin", "trustos_admin"] },
   { href: "/footprint", icon: Search, label: "Digital Footprint" },
   { href: "/reports", icon: FileText, label: "Audit Reports" },
 ];
@@ -40,7 +41,7 @@ export default function Sidebar() {
       {/* Nav */}
       <nav className="flex-1 px-3 py-4 overflow-y-auto">
         <div className="space-y-0.5">
-          {NAV.map(({ href, icon: Icon, label }) => {
+          {NAV.filter(item => !item.roles || (role && item.roles.includes(role))).map(({ href, icon: Icon, label }) => {
             const active = pathname === href || pathname.startsWith(href + "/");
             return (
               <Link