Initial commit: MikroTik btest server & client in Rust

Full reimplementation of the MikroTik Bandwidth Test protocol:
- Server mode: accepts connections from MikroTik devices on port 2000
- Client mode: connects to MikroTik btest servers
- TCP and UDP protocols with bidirectional support
- MD5 challenge-response authentication
- Dynamic speed adjustment (1.5x algorithm)
- Status exchange matching original C pselect() behavior
- Docker support with multi-stage build

Tested against MikroTik RouterOS achieving:
- 1.05 Gbps server RX (single connection)
- 530 Mbps client TCP download
- 840 Mbps client TCP upload
- 433 Mbps client UDP download

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

docker-compose.yml

@@ -0,0 +1,22 @@
+services:
+  btest-server:
+    build: .
+    container_name: btest-server
+    ports:
+      - "2000:2000/tcp"
+      - "2001-2100:2001-2100/udp"
+      - "2257-2356:2257-2356/udp"
+    command: ["-s", "-v"]
+    restart: unless-stopped
+
+  # Server with authentication enabled
+  btest-server-auth:
+    build: .
+    container_name: btest-server-auth
+    ports:
+      - "2010:2000/tcp"
+      - "2101-2200:2001-2100/udp"
+    command: ["-s", "-a", "admin", "-p", "password", "-v"]
+    restart: unless-stopped
+    profiles:
+      - auth