[refactor](decoders): extract decoder logging into trx-decode-log crate

Move DecoderLoggers and DecodeLogsConfig out of trx-server into a
dedicated src/decoders/trx-decode-log crate, giving file logging the
same standalone crate treatment as the four decoder crates.

- src/decoders/trx-decode-log/ (new — DecodeLogsConfig + DecoderLoggers)
- trx-server/config.rs: re-exports DecodeLogsConfig from trx-decode-log
  so ServerConfig field references and all tests compile unchanged
- trx-server: drop decode_logs module, use trx_decode_log directly

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -2343,6 +2343,18 @@ dependencies = [
  "trx-core",
 ]
 
+[[package]]
+name = "trx-decode-log"
+version = "0.1.0"
+dependencies = [
+ "chrono",
+ "dirs",
+ "serde",
+ "serde_json",
+ "tracing",
+ "trx-core",
+]
+
 [[package]]
 name = "trx-frontend"
 version = "0.1.0"
@@ -2433,6 +2445,7 @@ dependencies = [
  "trx-backend",
  "trx-core",
  "trx-cw",
+ "trx-decode-log",
  "trx-ft8",
  "trx-protocol",
  "trx-wspr",