feat(admin): live redis kill-switch on tunnel actions, sortable columns + CSV export + bulk actions, Node 24 LTS

WS1: pin all Docker stages to node:24.16.0-alpine; add engines node>=20.
WS2: lib/redis.ts gains TTL-backed redisSet, redisDel, setTunnelActive (writes tunnel:active:<sub>=1/0 EX 30, TUNNEL_ACTIVE_TTL override, no-op without REDIS_URL); wired into tunnel active/delete/reassign routes.
WS3: sortable columns, CSV export routes (token excluded), and bulk actions (self-account guard) across users/tunnels/audit admin tables.

Dockerfile

@@ -1,12 +1,12 @@
 # syntax=docker/dockerfile:1.7
 
-FROM node:20.18.0-alpine AS deps
+FROM node:24.16.0-alpine AS deps
 WORKDIR /app
 RUN apk add --no-cache libc6-compat
 COPY package.json ./
 RUN npm install --no-audit --no-fund --loglevel=error
 
-FROM node:20.18.0-alpine AS builder
+FROM node:24.16.0-alpine AS builder
 WORKDIR /app
 ENV NEXT_TELEMETRY_DISABLED=1
 COPY --from=deps /app/node_modules ./node_modules
@@ -20,7 +20,7 @@ ENV NEXT_PUBLIC_SUPABASE_URL=$NEXT_PUBLIC_SUPABASE_URL \
     NEXT_PUBLIC_APP_URL=$NEXT_PUBLIC_APP_URL
 RUN npm run build
 
-FROM node:20.18.0-alpine AS runner
+FROM node:24.16.0-alpine AS runner
 WORKDIR /app
 ENV NODE_ENV=production \
     NEXT_TELEMETRY_DISABLED=1 \