perf: sync protocol and core hardening updates

deploy/migrations/0078_channel_send_fingerprint.up.sql

@@ -0,0 +1,16 @@
+-- Persist the immutable client intent beside a channel random_id receipt.
+--
+-- The empty default is intentional for rolling deploys: binaries that predate
+-- this migration can continue to insert channel/service messages.  Empty
+-- fingerprints are legacy/unknown receipts and the replay path rejects them;
+-- it never guesses intent from an editable message projection.
+ALTER TABLE public.channel_messages
+    ADD COLUMN request_fingerprint bytea NOT NULL DEFAULT '\x';
+
+ALTER TABLE public.channel_messages
+    ADD CONSTRAINT channel_messages_request_fingerprint_size
+    CHECK (octet_length(request_fingerprint) IN (0, 32)) NOT VALID;
+
+-- NOT VALID avoids a blocking historical-table validation scan during the
+-- rolling migration while PostgreSQL still enforces the check for every new
+-- or updated row. A later maintenance window may validate it online.