Give every view a TSIG key that selects it

Each view's match-clients starts with "key jarl-view-NAME" (after
"!key" for the views listed after it), so a query signed with a view's
key lands in that view from any address. The secrets are derived from a
random seed in Jarl's database. The delegation check signs its queries
to this server's own addresses with the key of the zone's view: before,
they got whichever view matched the server's address, usually internal.
jarl view key / GET /views/{id}/key show a key for dig -k (tsig:write,
audited). jarl-view- key names are reserved; the importer drops view
keys from a configuration Jarl wrote.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/render/stats.go

@@ -15,6 +15,9 @@ type Extras struct {
 	// Stats, when set, makes named publish what Jarl's statistics
 	// collector reads.
 	Stats *StatsHooks
+	// ViewKeySeed, when set, gives every view a TSIG key that selects it
+	// (viewkeys.go).
+	ViewKeySeed []byte
 }
 
 // StatsHooks describe the statistics channel and response log Jarl needs.