luci-app-adblock-fast: update to 1.2.4-2

luci-app-adblock-fast: update to 1.2.4-2

Maintainer: me
Compile tested: x86_64, Dell EMC Edge620, OpenWrt 25.12.4
Run tested: x86_64, Dell EMC Edge620, OpenWrt 25.12.4

Description:
Update to 1.2.4-2

  - Update PKG_VERSION to 1.2.4 and PKG_RELEASE to 2.

README.md:
  - Update documentation URL from melmac.ca to mossdef.org.

htdocs/luci-static/resources/adblock-fast/status.js:
  - Update `pkg.LuciCompat` to 17.
  - Add `pkg.ChromeExtensionId` for the companion browser extension.
  - Update documentation URLs from melmac.ca to mossdef.org.
  - Add new warning messages for throttled parallel downloads and download
    timeouts.
  - Update `errorDetectingFileType` message to include the filename.
  - Update `syncCron` RPC: it now accepts schedule parameters (e.g.,
    `auto_update_enabled`, `auto_update_mode`) as distinct arguments instead
    of relying on UCI. The cron line is assembled and validated server-side.
  - Remove `setCronEntry` RPC, replaced by the extended `syncCron`.
  - Wrap `_syncCron` with a `syncCron` helper function that translates the
    schedule object into discrete arguments for the RPC call.

htdocs/luci-static/resources/view/adblock-fast/overview.js:
  - Add `maybeNagChromeExtension` to detect the AdBlock-Fast Controller
    Chrome extension and nag if missing.
  - Remove `generateCronEntry` helper function: the cron line is now
    assembled server-side.
  - Mark auto_update_* form fields as virtual: they are displayed from parsed
    cron data and submitted via `syncCron`, but never written to UCI.
  - Add new advanced options for download: `download_connect_timeout`,
    `download_max_time`, and `download_allow_insecure`.
  - Update `parallel_downloads` to be a range (1-16) instead of a boolean
    flag, with a default of 8. The label now indicates automatic reduction
    with low memory.
  - Modify `handleSave` and `handleSaveApply` to collect schedule data and
    pass it to `adb.syncCron` as discrete fields, bypassing UCI writes for
    scheduling. This ensures the crontab is the single source of truth for
    the schedule.

root/etc/uci-defaults/40_luci-adblock-fast:
  - Add logic to remove stale `auto_update_*` UCI keys from older versions,
    as the cron schedule is no longer mirrored in UCI.

root/usr/share/rpcd/acl.d/luci-app-adblock-fast.json:
  - Remove `setCronEntry` from ACL, as it has been replaced by `syncCron`.

root/usr/share/rpcd/ucode/luci.adblock-fast:
  - Update `rpcdCompat` to 17.
  - Remove explicit `setCronEntry` call from the example section.
  - Update `syncCron` example: it now includes schedule parameters, replacing
    `setCronEntry`.
  - Add `cron_field` helper function to coerce schedule fields to bounded
    integers, providing security against injection into crontabs.
  - Add `CRON_MODES` constant to allowlist accepted scheduling modes.
  - Update `cron_write` to accept `schedule` object with discrete fields.
    It now parses existing cron lines to preserve the schedule on state-only
    changes and validates all fields through `cron_field`/`CRON_MODES`.
  - Rename `get_cron_status` to `cron_read`, reflecting its read-only nature.
  - Update `cron_read` to parse the crontab line and return the schedule as
    strings, eliminating reliance on UCI for schedule configuration. The UI
    now parses this entry for display.
  - Refactor cron management functions (`update_cron`, `get_cron_status`)
    for improved security, robustness, and to remove UCI as a source of
    truth for cron schedule.

Signed-off-by: Stan Grishin <redacted>