feat(postal): add postal service addon and bundle pending addon work

- New postal-service-addon: per-player mailboxes + post-office send block
  (ActionForm recipient picker, offline notification queue, chunk-load
  retry via tickingarea)
- Commit previously untracked private-chest, home-sign, keep-inventory
  addons and their docker-compose mounts
- Deploy workflow: add postal + previously unwired addons to path filter
  and checkout list; drop easter-egg from deployment
- enabled_packs.json: register postal UUIDs for Lyla + Mya

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

keep-inventory-addon/keep_inventory_BP/manifest.json

@@ -0,0 +1,30 @@
+{
+  "format_version": 2,
+  "header": {
+    "name": "Keep Inventory",
+    "description": "Asserts gamerule keepInventory true on world load (Lyla's world)",
+    "uuid": "b4d72e91-8c43-4f1a-95d2-7e3b6c8a0d10",
+    "version": [1, 0, 0],
+    "min_engine_version": [1, 21, 0]
+  },
+  "modules": [
+    {
+      "type": "data",
+      "uuid": "b4d72e91-8c43-4f1a-95d2-7e3b6c8a0d11",
+      "version": [1, 0, 0]
+    },
+    {
+      "type": "script",
+      "language": "javascript",
+      "uuid": "b4d72e91-8c43-4f1a-95d2-7e3b6c8a0d12",
+      "version": [1, 0, 0],
+      "entry": "scripts/main.js"
+    }
+  ],
+  "dependencies": [
+    {
+      "module_name": "@minecraft/server",
+      "version": "1.17.0"
+    }
+  ]
+}

keep-inventory-addon/keep_inventory_BP/scripts/main.js

@@ -0,0 +1,17 @@
+import { world, system } from "@minecraft/server";
+
+function assertKeepInventory() {
+  try {
+    world.getDimension("overworld").runCommand("gamerule keepInventory true");
+  } catch (e) {
+    // Non-fatal — chunk-load races, etc. The next interval will retry.
+  }
+}
+
+system.run(() => {
+  assertKeepInventory();
+  world.sendMessage("§a[Keep Inventory] §7keepInventory enforced — items stay on death.");
+});
+
+// Re-assert every 10 minutes so anything that toggles it off (manual op, world reset, etc.) gets corrected.
+system.runInterval(assertKeepInventory, 12000);