Wi-Fi Tools: scan logging to CSV, plus sort and filter

- lib/wifi (host-tested): scan_log (CSV field quoting, header/row, a
  once-per-interval throttle) and network_list_view (sort by signal /
  channel / name, filter open-only / hide-hidden / strong-only)
- ScanEntry moved to lib/wifi so both are testable on the PC
- Wi-Fi Tools networks view: s sort, o/h/w filters, l toggles logging
  to /wifi/scans/<date>.csv (header + one row per AP per logged scan,
  throttled 30 s, needs the clock for timestamps); foreground-only
- Wi-Fi scan logs replace probe-request logs as a clean-up category
- Serial: cat <path>, and key <char> injects a character

Verified on the device: CSV written with header, timestamps, BSSID,
channel, RSSI, security and SSID; hidden networks marked.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

CONTEXT.md

@@ -91,7 +91,7 @@ The `opt` key used as a dead key. Pressing it and then a base letter types an ac
 _Avoid_: modifier, alt
 
 **Log**:
-History the device records automatically in the background: mesh message history, IRC logs, probe-request logs.
+History the device records automatically in the background: mesh message history, IRC logs, Wi-Fi scan logs.
 _Avoid_: history file, dump
 
 **Capture**: