fix: Reduce amount of rescans in giant $HOME like folders - #751

Upstream (6 commits): rescan throttling for giant folders (dmtrKovalenko#751), configurable
$HOME scanning (dmtrKovalenko#743/dmtrKovalenko#749), Lua-level fs-root/home guard (dmtrKovalenko#745/dmtrKovalenko#748), pi-fff
SDK import cache (dmtrKovalenko#758), release 0.10.3.

Conflict resolution:
- Cargo.toml/Cargo.lock (all crates): keep fork's 0.17.2 version scheme over
  upstream's 0.10.3; preserve fff-mcp's fff-ipc/dirs/libc deps and upstream's
  new rescan-stats feature.
- Makefile: union of fork's daemon/install targets and upstream's
  test-rescan/rescan-probe targets.
- install-mcp.sh: keep fork's removal of the pinned-release SHA block
  (delivery is via Homebrew tap + apt, not pinned GitHub tarballs).
- background_watcher.rs: adopt upstream's throttled try_trigger_full_rescan
  mechanism wholesale, keeping only the fork's per-root user_gi ignore filter;
  drop the obsolete need_full_rescan boolean.

First stable release since 0.17.2. Rolls up the fork's Linux APT delivery
pipeline, the worker bootstrap thundering-herd fix, the watcher lock-order
hardening, the macOS git-status staleness fix, and three upstream syncs —
empty-dir scan (dmtrKovalenko#735), gitignore fix (dmtrKovalenko#744), pi-fff dedup (dmtrKovalenko#750), and
rescan throttling for giant folders (dmtrKovalenko#751).