sysinfo.sh: MLO sta count via hostapd_cli + ifname-in-config fallback

[perceival]

Summary

Two real fixes for misc/sysinfo.sh on modern OpenWrt / GL.iNet builds, plus some
header cleanup. Tested on GL.iNet BE9300 (Flint 3) running OpenWrt 23.05-SNAPSHOT
with MLO across wlan02 / wlan12 / wlan22, and on two older APs
(Netgear R7800 and Linksys E8450) running vanilla OpenWrt.

1. ubus network.wireless status schema move — ifname now lives inside config

On newer OpenWrt, ubus call network.wireless status no longer exposes
ifname at the per-interface object level — it has moved into the inner
config object. The current code only reads the top-level value, so
$RadioIface ends up empty, the per-iface code path is skipped, and the
output silently degrades to conn: Down for every radio.

Fix: read the top-level first (back-compat with older builds), then fall
back to config.ifname if it's empty.

2. iw dev <ifname> station dump misses MLO/MLD-bound stations

On Wi-Fi 7 hardware with MLO enabled, clients associated through an MLD
do not show up in iw dev <radio> station dump — the kernel reports
them per-link only via hostapd's control socket. As a result, the
station counter shows 0 / wrong values on Flint 3 etc.

Added get_sta_count() helper that prefers hostapd_cli ... status and
sums num_sta[*] across BSS slots:

1. hostapd_cli -p /var/run/hostapd -i $iface status (single-dir layout, stock OpenWrt)
2. hostapd_cli -p /var/run/hostapd-$iface -i $iface status (per-instance dir layout)
3. fallback: original iw dev $iface station dump | grep -c '^Station'

Counts now match hostapd_cli status num_sta and the LuCI overview.

3. Header cleanup (commit 2)

• Restored the original Polish revision-log entries from upstream and
  kept English translations side-by-side (PL / EN per line). The file
  is now valid UTF-8 — the original had mixed ISO-8859-2 / CP1250 bytes
  so ś rendered as ¶ / œ depending on terminal.
• Updated # Destination hint from /sbin/sysinfo.sh to
  /etc/profile.d/99-sysinfo.sh, which is where the script naturally
  fires on modern OpenWrt (runs on each shell login, survives sysupgrade
  when listed in /etc/sysupgrade.conf).

Other changes already in perceival:master

Two smaller pre-existing changes from my fork's master also flow into this PR
because they sit on the same path; flagging them so they aren't lost in review:

• clean_output() filter that strips literal e[0;31m / e[0m strings that
  some logread outputs leak when not on a TTY (applied via
  print_error | clean_output).
• print_lan() now skips zones that have no DHCP pool configured
  (uci get dhcp.$Device.start empty) — previously they printed an empty
  dhcp: n/a row. Also references dhcp.$Device.{start,limit} directly
  instead of the dhcp.@dhcp[*].interface=$Device lookup, since the latter
  doesn't match named DHCP sections on current OpenWrt configs.

Happy to split these out into a separate PR if you'd prefer.

Test plan

• Flint 3 / BE9300, OpenWrt 23.05-SNAPSHOT, MLO across 2.4/5/6 GHz —
  conn: now matches hostapd_cli status num_sta and LuCI client count
• Older GL.iNet APs (no MLO) — conn: still matches iw dev fallback
• sh -n misc/sysinfo.sh clean
• HTML mode (REQUEST_METHOD=GET sysinfo.sh) still renders
• (Maintainer) Verify on stock OpenWrt 23.05 / 24.10 reference image

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