Adventure news: fix posting gates, digest counts, and section gating

- Don't post adventure beats when posting.enabled=false (PostNow ignores the flag)
- Keep the adventure channel out of the round-robin rotation so it can't steal bulletins from the digest
- no_push now retires a fact against the digest, not just the live post
- Default a missing occurred_at to now instead of the Unix epoch
- Keep protocol-relative image URLs on the guarded thumbnailer
- Make digest_hour=0 (midnight UTC) settable
- Quote the true window total in the digest, not the truncated slice
- Hide the Adventure section entirely when it's disabled

internal/web/thumbs.go

@@ -69,8 +69,10 @@ func thumbURL(src string) string {
 	}
 	// Root-relative sources are our own local assets (e.g. the adventure
 	// emblems) — serve them directly; the thumbnailer only handles remote
-	// http(s) images and would 404 a local path.
-	if strings.HasPrefix(src, "/") {
+	// http(s) images and would 404 a local path. "//host/x.jpg" is NOT local:
+	// it's a protocol-relative remote image, and it has to keep going through
+	// the guarded thumbnailer like any other third-party URL.
+	if strings.HasPrefix(src, "/") && !strings.HasPrefix(src, "//") {
 		return src
 	}
 	return "/img/" + thumbKey(src) + ".avif?u=" + url.QueryEscape(src)