feat: Replace SQM with per-client speed control for paid WiFi upgrade

Add parahub-speed-control script (nftables set + tc HTB) for per-IP
speed shaping. Free tier 512kbps, paid tier unlimited. Heartbeat now
parses paid_clients from API response and syncs nftables set.

Replaced sqm-scripts/kmod-sched-cake/luci-app-sqm packages with
tc-full/kmod-ifb/kmod-sched-htb. Section 8 of uci-defaults creates
init.d service for speed control instead of SQM config.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/build.sh

@@ -86,10 +86,10 @@ PACKAGES_BUMBLEBEE=(
     wireguard-tools
     luci-proto-wireguard
     https-dns-proxy
-    sqm-scripts
-    kmod-sched-cake
+    tc-full
+    kmod-ifb
+    kmod-sched-htb
     luci
-    luci-app-sqm
     tcpdump
     iperf3
     iwinfo