draggable topology + attack visualizer + tools in containers

- topology nodes draggable (pointer events, SVG transform), layout hint shown
- attack visualizer: /api/attacks logs attacker->target events; red pulsing
  dashed arcs on recent attacks (60s hot), ⚔ counts ok/fail
- submit_flag now takes attacker_idx vs target_idx (A/D semantics); UI has
  target dropdown (enemy teams), leaderboard records target
- containers get vim+curl+wget+netcat+git+pip3 (Dockerfiles blogpost/cdn/
  phew/sheesh/warmup); warmup base ubuntu:20.04 EOL -> 24.04
- team portal: target dropdown refreshed after login (was empty pre-auth)

services/cdn/Dockerfile

@@ -22,6 +22,12 @@ RUN apt-get update && \
       build-essential \
       bash \
       nano \
+      vim \
+      curl \
+      wget \
+      netcat-openbsd \
+      git \
+      python3-pip \
     && rm -rf /var/lib/apt/lists/*
 
 # Create an unprivileged user for running the app / SSH access