Live ops wall + pluggable camera providers with licence gating (server-26#198)

Backend (c2-core):
- app/internal/cameras/: provider interface, licence model, per-provider
  catalog cache; one adapter per source in design-canvas/camera-sources.md.
  Implemented: 511NY (legacy shape + tolerant XML inventory parser, 511x
  endpoints UNVERIFIED), Caltrans, DelDOT, Ontario 511, DriveBC, Calgary,
  TfL, NSW, Fintraffic. Stubs: NYC DOT, Westchester DPW, TRANSCOM, CTroads,
  511NJ, Austin, TxDOT, MD CHART, WSDOT, Tallinn, Tarktee, Warendorf,
  TrafficLand, Windy, EarthCam.
- Every provider defaults OFF (config/camera_providers). Gated licences
  (agreement required / unverified / non-commercial / paid) need an explicit
  acknowledgement stored with who/when and written to audit_log; the audit
  write is a precondition. Stubs and prohibited sources cannot be enabled.
  Ack is bound to the licence status it was given for.
- GET /cameras (signed-in), GET/PUT /admin/camera-providers (admin only).
- /traffic/511 follows the ny511 provider switch and returns the DAA credit
  + NYSDOT as-is disclaimer; 511NY event descriptions no longer truncated
  ("may not alter the substance of a report").

Frontend:
- LiveView becomes the ops wall: Region > Incident > Camera drill-down,
  worst-first rail (MapView), KPIs, transcript ticker, scrubber incident
  bands, auto-tour, deep links (#inc=&cam=&tour), Esc steps up.
- Incident panel: nearest cameras (path-weighted), fused situational context
  (ADS-B, AIS, 511NY events, NEXRAD tile sample), units, call spine.
- MapView keeps every layer; adds Camera Viewsheds (approx.) overlay and a
  nearest-camera layer for the selected incident.
- CameraFeed hygiene: hidden-tab/off-screen gating, 2 concurrent HLS cap,
  last good frame + stale badge, frozen-frame signature, HLS stall watchdog,
  provider attribution rendered on the imagery.
- Camera/event popups show source credit, update time and the disclaimer.
- Admin > Camera providers tab with licence status, health, gated confirm.
- Camera detection is not built (blocked on #199/#200); seam only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/app/admin/page.tsx

@@ -3,6 +3,7 @@
 import { useAuth } from "@/components/AuthProvider";
 import { c2api } from "@/lib/c2api";
 import { ReplayTab } from "@/components/admin/ReplayTab";
+import { CameraProvidersTab } from "@/components/admin/CameraProvidersTab";
 import { useEffect, useState, useRef, useCallback } from "react";
 import { useRouter } from "next/navigation";
 import type { UserRecord, AuditEntry, UserRole, CallRecord } from "@/lib/types";
@@ -1267,10 +1268,11 @@ function SttEvalTab() {
 // Main admin page
 // ---------------------------------------------------------------------------
 
-type AdminTab = "features" | "correlation" | "replay" | "users" | "audit" | "calls" | "eval";
+type AdminTab = "features" | "cameras" | "correlation" | "replay" | "users" | "audit" | "calls" | "eval";
 
 const TAB_LABELS: { key: AdminTab; label: string }[] = [
   { key: "features",    label: "AI Features" },
+  { key: "cameras",     label: "Camera providers" },
   { key: "correlation", label: "Correlation Debug" },
   { key: "replay",      label: "Replay" },
   { key: "calls",       label: "Calls" },
@@ -1297,7 +1299,7 @@ export default function AdminPage() {
   if (!isAdmin) return null;
 
   // Users/Audit tabs benefit from full width; everything else is narrow
-  const wide = tab === "users" || tab === "audit" || tab === "replay";
+  const wide = tab === "users" || tab === "audit" || tab === "replay" || tab === "cameras";
 
   return (
     <div className={`space-y-6 ${wide ? "" : "max-w-2xl"}`}>
@@ -1318,6 +1320,7 @@ export default function AdminPage() {
       </div>
 
       {tab === "features"    && <FeaturesTab />}
+      {tab === "cameras"     && <CameraProvidersTab />}
       {tab === "correlation" && <CorrelationDebugTab />}
       {tab === "replay"      && <ReplayTab />}
       {tab === "calls"       && <StaleCallsTab />}