fix(addons): correct recipe unlock shape and block format_version

Follow-up to 4324882. The { "context": "always_unlocked" } form triggered
"malformed unlocking context" on 1.26-series Bedrock (AlwaysUnlocked pascal
form fared no better). Empty-array form is the universally accepted "recipe
always known" shape. This unblocks mc-lobby which was crashing on boot.

Also reverts block format_version on mailbox.json + smart_crafting_table.json
to 1.21.0 — every other working block in the repo uses that, so the prior
1.21.60 choice was unnecessary.

- 19 dragon + portal recipes (spark_pet_BP, lobby_transfer_BP): unlock -> []
- 7 other recipes touching unlock { context: ... }: same
- 2 block files: format_version 1.21.60 -> 1.21.0

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

addon/spark_pet_BP/recipes/dragon_egg.json

@@ -4,21 +4,29 @@
     "description": {
       "identifier": "silverlabs:dragon_egg"
     },
-    "unlock": { "context": "always_unlocked" },
-    "tags": ["crafting_table"],
+    "unlock": [],
+    "tags": [
+      "crafting_table"
+    ],
     "pattern": [
       " B ",
       "AGA",
       " A "
     ],
     "key": {
-      "B": { "item": "minecraft:blaze_powder" },
-      "A": { "item": "minecraft:amethyst_shard" },
-      "G": { "item": "minecraft:gold_ingot" }
+      "B": {
+        "item": "minecraft:blaze_powder"
+      },
+      "A": {
+        "item": "minecraft:amethyst_shard"
+      },
+      "G": {
+        "item": "minecraft:gold_ingot"
+      }
     },
     "result": {
       "item": "silverlabs:dragon_egg",
       "count": 1
     }
   }
-}
+}