Initial commit: LibreDrive unlocker plugin for libfreemkv

New crate freemkv-unlock-ld — the LibreDrive Unlocker implementation,
split out of libfreemkv so the library stays firmware-clean on crates.io.

Owns everything about HOW MediaTek MT1959 drives are firmware-unlocked:
  - profiles.json (the bundled drive-profile database + DriveProfile parse)
  - src/platform/mt1959/* (variant-A/B firmware upload + unlock handshake)
  - WRITE_BUFFER / MODE SELECT upload, unlock CDBs, disc-speed calibration

Exposes LibreDrive::new() implementing libfreemkv::Unlocker (name/matches/
unlock). Plug it in with one line at process start:

  libfreemkv::register_unlocker(Box::new(freemkv_unlock_ld::LibreDrive::new()));

Depends on libfreemkv (path-patched via gitignored .cargo/config.toml in
dev) for the trait, ScsiTransport, DriveId, and Result. README notes it's
the LibreDrive unlocker (attribution to be added by owner).

Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "freemkv-unlock-ld"
+version = "1.0.0-rc.2"
+edition = "2024"
+rust-version = "1.86"
+license = "AGPL-3.0-only"
+description = "LibreDrive unlocker plugin for libfreemkv (firmware unlock for MediaTek MT1959 drives)"
+repository = "https://github.com/freemkv/freemkv-unlock-ld"
+
+[dependencies]
+libfreemkv = "1.0.0-rc.2"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+base64 = "0.22.1"
+tracing = "0.1"