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>

scripts/test-mikrotik.sh

@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+# Test against a MikroTik device
+# Usage: ./scripts/test-mikrotik.sh <mikrotik_ip> [username] [password]
+set -euo pipefail
+
+MIKROTIK_IP="${1:?Usage: $0 <mikrotik_ip> [username] [password]}"
+USERNAME="${2:-}"
+PASSWORD="${3:-}"
+BTEST="./target/release/btest"
+
+echo "=== Building release binary ==="
+cargo build --release
+
+AUTH_ARGS=""
+if [ -n "$USERNAME" ]; then
+    AUTH_ARGS="-a $USERNAME"
+fi
+if [ -n "$PASSWORD" ]; then
+    AUTH_ARGS="$AUTH_ARGS -p $PASSWORD"
+fi
+
+echo ""
+echo "=== Testing against MikroTik at $MIKROTIK_IP ==="
+echo ""
+
+TIMEOUT_CMD="timeout"
+if ! command -v timeout &>/dev/null; then
+    if command -v gtimeout &>/dev/null; then
+        TIMEOUT_CMD="gtimeout"
+    else
+        TIMEOUT_CMD=""
+    fi
+fi
+
+run_test() {
+    local desc="$1"
+    shift
+    echo "--- $desc ---"
+    if [ -n "$TIMEOUT_CMD" ]; then
+        $TIMEOUT_CMD 10 $BTEST "$@" $AUTH_ARGS || echo "(test ended)"
+    else
+        $BTEST "$@" $AUTH_ARGS &
+        local pid=$!
+        sleep 10
+        kill $pid 2>/dev/null || true
+        wait $pid 2>/dev/null || true
+        echo "(test ended)"
+    fi
+    echo ""
+    sleep 1
+}
+
+echo "=== Mode 1: Our client -> MikroTik btest server ==="
+echo "(Make sure btest server is enabled on your MikroTik: /tool/bandwidth-server set enabled=yes)"
+echo ""
+
+run_test "TCP Download from MikroTik" -c "$MIKROTIK_IP" -r
+run_test "TCP Upload to MikroTik" -c "$MIKROTIK_IP" -t
+run_test "TCP Bidirectional with MikroTik" -c "$MIKROTIK_IP" -t -r
+run_test "UDP Download from MikroTik" -c "$MIKROTIK_IP" -r -u
+run_test "UDP Upload to MikroTik" -c "$MIKROTIK_IP" -t -u
+
+echo ""
+echo "=== Mode 2: Our server <- MikroTik connects to us ==="
+echo "To test this mode:"
+echo "  1. Run:  $BTEST -s -v $AUTH_ARGS"
+echo "  2. On MikroTik, run:"
+echo "     /tool/bandwidth-test address=<this_server_ip> direction=both protocol=tcp"
+echo ""
+echo "=== All MikroTik tests completed ==="