[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>

src/decoders/trx-decode-log/Cargo.toml

@@ -0,0 +1,16 @@
+# SPDX-FileCopyrightText: 2026 Stanislaw Grams <stanislawgrams@gmail.com>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+
+[package]
+name = "trx-decode-log"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+trx-core = { path = "../../trx-core" }
+chrono = { version = "0.4", default-features = false, features = ["clock"] }
+dirs = "6"
+serde = { workspace = true, features = ["derive"] }
+serde_json = { workspace = true }
+tracing = { workspace = true }