floonet-rs: hardened nostr-rs-relay for the Grin community

nostr-rs-relay + a default-deny admission pipeline (kinds 0,3,5,13,1059,
10002,10050,27235 only), NIP-42 auth, neutral NIP-11, a built-in name
authority (paid names via GoblinPay), and a config-toggled co-located
mixnet exit supervisor. Single binary + installer + hardened systemd, or
Docker Compose. Relay core untouched (additive admission + authority).

.gitignore

@@ -0,0 +1,6 @@
+**/target/
+nostr.db
+nostr.db-*
+justfile
+result
+**/.idea/