Add OpenWrt ipk packaging + split client/server binaries

OpenWrt package (deploy/openwrt/):
- build-ipk.sh: creates .ipk from pre-built binary (no SDK needed)
- Makefile: for OpenWrt SDK integration
- ProCD init script with UCI config
- Supports all architectures (x86_64, aarch64, mipsel, mips)

Split binaries for embedded (src/bin/):
- btest-client: client-only, no server/syslog/csv
- btest-server: server-only, no client
- release-small profile: opt-level=z + panic=abort

Sizes (compressed .tar.gz):
  Full btest:    ~1 MB
  btest-client:  ~500 KB (release-small)
  btest-server:  ~550 KB (release-small)

Install on OpenWrt:
  opkg install btest-rs_0.6.0-1_x86_64.ipk

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

deploy/openwrt/Makefile

@@ -0,0 +1,57 @@
+# OpenWrt package Makefile for btest-rs
+#
+# To build:
+#   1. Clone the OpenWrt SDK for your target
+#   2. Copy this directory to package/btest-rs/ in the SDK
+#   3. Run: make package/btest-rs/compile V=s
+#
+# Or use the pre-built binary approach (see build-ipk.sh)
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=btest-rs
+PKG_VERSION:=0.6.0
+PKG_RELEASE:=1
+
+PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
+PKG_SOURCE_URL:=https://github.com/manawenuz/btest-rs/archive/refs/tags/v$(PKG_VERSION).tar.gz
+PKG_HASH:=skip
+
+PKG_BUILD_DEPENDS:=rust/host
+PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)-$(PKG_VERSION)
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/btest-rs
+  SECTION:=net
+  CATEGORY:=Network
+  TITLE:=MikroTik Bandwidth Test server and client
+  URL:=https://github.com/manawenuz/btest-rs
+  DEPENDS:=
+  PKGARCH:=$(ARCH)
+endef
+
+define Package/btest-rs/description
+  A Rust reimplementation of the MikroTik Bandwidth Test (btest) protocol.
+  Supports TCP/UDP, IPv4/IPv6, EC-SRP5 and MD5 authentication,
+  multi-connection, syslog, CSV output, and CPU monitoring.
+endef
+
+define Build/Compile
+	cd $(PKG_BUILD_DIR) && \
+	CARGO_TARGET_DIR=$(PKG_BUILD_DIR)/target \
+	cargo build --release --target $(RUSTC_TARGET)
+endef
+
+define Package/btest-rs/install
+	$(INSTALL_DIR) $(1)/usr/bin
+	$(INSTALL_BIN) $(PKG_BUILD_DIR)/target/$(RUSTC_TARGET)/release/btest $(1)/usr/bin/btest
+
+	$(INSTALL_DIR) $(1)/etc/init.d
+	$(INSTALL_BIN) ./files/btest.init $(1)/etc/init.d/btest
+
+	$(INSTALL_DIR) $(1)/etc/config
+	$(INSTALL_CONF) ./files/btest.config $(1)/etc/config/btest
+endef
+
+$(eval $(call BuildPackage,btest-rs))