feat(mini): add compact native EasyTier client (#2479)

Add a native EasyTier proof-of-concept binary with TCP and UDP
transports, TUN, UDP hole punching, AES-GCM, and a read-only RPC
portal.

Introduce a release-derived mini profile and musl linker policy so
x86_64, big-endian MIPS, and little-endian MIPS stay below the strict
5,000,000-byte target without UPX.

easytier-contrib/easytier-mini/easytier-mini-musl.ld

@@ -0,0 +1,14 @@
+SECTIONS
+{
+  .eh_frame :
+  {
+    KEEP(*crtbegin.o(.eh_frame))
+    KEEP(*crtend.o(.eh_frame))
+  }
+  /DISCARD/ :
+  {
+    *(EXCLUDE_FILE (*crtbegin.o *crtend.o) .eh_frame)
+    *(.eh_frame_hdr)
+  }
+}
+INSERT AFTER .data;