switch nginx-vod-module to the maintained dio-az fork (#24123)

The `v1.x` line is the same muxed fMP4 code as Kaltura's 1.31 with fixes backported, so the mapping JSON, manifest routes, and ffmpeg consumers are unchanged. The `MAX_CLIPS` patch applies as-is and the HEVC workaround is rewritten for the fork's reformatted source.

`vod_hls_version 6` is now explicit because the fork replaced Kaltura's automatic version calculation with a directive that defaults to 4 and only warns when fmp4 needs 6, so playlists were being stamped `EXT-X-VERSION:4` while carrying `EXT-X-MAP`. The `error_page 502 =404` hack is gone: https://github.com/kaltura/nginx-vod-module/issues/468 is a `vod_mode remote` bug and we're `mapped`, so those 502s were really `_vod_response` returning 404 upstream. The fork maps that through now, and the hack was also turning real 5xx into "no recordings".

docker/main/rootfs/usr/local/nginx/conf/nginx.conf

@@ -122,6 +122,10 @@ http {
             # Smaller segments, faster generation, better browser compatibility
             vod_hls_container_format fmp4;
 
+            # fMP4 playlists use EXT-X-MAP, which requires HLS protocol
+            # version 6 (RFC 8216 section 7); the module default is 4
+            vod_hls_version 6;
+
             secure_token $args;
             secure_token_types application/vnd.apple.mpegurl;
 
@@ -130,14 +134,6 @@ http {
             expires off;
 
             keepalive_disable safari;
-
-            # vod module returns 502 for non-existent media
-            # https://github.com/kaltura/nginx-vod-module/issues/468
-            error_page 502 =404 /vod-not-found;
-        }
-
-        location = /vod-not-found {
-            return 404;
         }
 
         location /stream/ {