Fix gamerule toggles for 26.x renames; add map/skins/pregen + admin favors

Minecraft 26.x renamed every gamerule to snake_case (keepInventory →
keep_inventory, doDaylightCycle → advance_time, ...), so the panel's
queries hit unknown rules: reads returned nothing, toggles always
started from 'off', and sets silently failed. Rules are now defined by
candidate names resolved against the live server (works on old and new
versions), sets are verified by re-query, and failures surface the
server's actual reply. Toggles render only for rules the server reports.

Creative additions:
- Featured mods on the Mods page: BlueMap (3D web map), SkinRestorer
  (real skins in offline mode), Chunky (pregen) — verified for 26.2
- BlueMap plumbing: MAP_PORT mapping in compose, in-network detection,
  'Open the live world map' link on the Overview
- Player modal favors: heal, teleport-to-player, give item
- Broadcast box gained a full-screen title mode

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.env.example

@@ -13,6 +13,8 @@ SERVER_TYPE=FABRIC
 MC_MEMORY=6G
 MC_CONTAINER_MEM_LIMIT=7g
 MC_PORT=25565
+# BlueMap web map port (used when the bluemap mod is installed)
+MAP_PORT=8100
 
 MC_MOTD=A cozy server for friends
 MC_DIFFICULTY=normal