[feat](trx-ftx): add pure Rust FTx decoder crate

Replace the C FFI-based trx-ft8 with a pure Rust implementation
supporting FT8, FT4, and FT2 protocols. Eliminates cc/libc build
dependencies and all unsafe FFI code while providing the same
Ft8Decoder/Ft8DecodeResult public API.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

Cargo.lock

@@ -1016,6 +1016,12 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
+[[package]]
+name = "hound"
+version = "3.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62adaabb884c94955b19907d60019f4e145d091c75345379e70d1ee696f7854f"
+
 [[package]]
 name = "http"
 version = "0.2.12"
@@ -1797,6 +1803,15 @@ dependencies = [
  "getrandom 0.3.4",
 ]
 
+[[package]]
+name = "realfft"
+version = "3.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f821338fddb99d089116342c46e9f1fbf3828dba077674613e734e01d6ea8677"
+dependencies = [
+ "rustfft",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.5.18"
@@ -2635,6 +2650,16 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "trx-ftx"
+version = "0.1.0"
+dependencies = [
+ "hound",
+ "num-complex",
+ "realfft",
+ "rustfft",
+]
+
 [[package]]
 name = "trx-protocol"
 version = "0.1.0"