v0.5.0: Add syslog support, fix TCP send/both, EC-SRP5 server auth

New features:
- --syslog <address:port> sends structured events to remote syslog (RFC 5424 UDP)
  Events: AUTH_SUCCESS, AUTH_FAILURE, TEST_START, TEST_END, TEST_RESULT
- EC-SRP5 authentication for both client and server modes
- TCP multi-connection support (session tokens, all 3 directions)

Bug fixes since v0.2.0:
- EC-SRP5 server: fixed gamma parity (was 50% auth failure rate)
- EC-SRP5 server: use lift_x not redp1 for verification
- TCP send direction: server sends 12-byte status messages to client
- TCP both direction: TX loop injects status between data packets
- TCP data: send all zeros (no 0x07 header that MikroTik rejected)
- TCP disconnect detection: running flag set on EOF
- UDP multi-connection: unconnected socket accepts all source ports

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "btest-rs"
-version = "0.3.0"
+version = "0.5.0"
 edition = "2021"
 description = "MikroTik Bandwidth Test (btest) server and client with EC-SRP5 auth — a Rust reimplementation"
 license = "MIT AND Apache-2.0"
@@ -31,6 +31,7 @@ num-bigint = "0.4.6"
 num-traits = "0.2.19"
 num-integer = "0.1.46"
 sha2 = "0.11.0"
+hostname = "0.4.2"
 
 [profile.release]
 opt-level = 3