feat(core,host): Wake-on-LAN sender + host MAC advertisement

Add a runtime-free Wake-on-LAN sender in punktfunk-core (per-interface subnet-directed broadcast + 255.255.255.255 on ports 9/7, repeated, optional last-known-IP unicast) exposed both as a Rust fn and a punktfunk_wake_on_lan C-ABI (ABI v3), plus a parse_mac helper. The host enumerates its wake-capable NIC MAC(s) and advertises them in a new mDNS `mac` TXT record (routed NIC first), and best-effort detects & warns (never modifies) when the NIC isn't armed for WoL.

MAC delivery is via the unauthenticated mDNS TXT rather than the connection handshake by design: a spoofed MAC only makes a wake fail (the packet is inert; the cert fingerprint still gates the connection), and it avoids threading through the hot connect path.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/Cargo.toml

@@ -21,6 +21,10 @@ tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 tracing-log = "0.2"
 axum = "0.8"
 mdns-sd = "0.20"
+# Wake-on-LAN: report the host's wake-capable NIC MAC(s) to clients via the mDNS `mac` TXT record.
+# `mac_address` reads a NIC's hardware address; `if-addrs` maps the routed IP to its interface name.
+mac_address = "1"
+if-addrs = "0.13"
 tokio = { version = "1", features = ["full"] }
 rsa = "0.9"
 sha2 = { version = "0.10", features = ["oid"] }