feat: make notifyBotToken/adminUserId optional

The client never sends pairing notifications (the server does); these
Discord fields were required but unused. Make them optional + drop from
the config schema's required list. Back-compat: still accepted if set.

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

package-lock.json

@@ -12,10 +12,14 @@
       },
       "devDependencies": {
         "@types/node": "^25.5.2",
+        "openclaw": "file:/usr/lib/node_modules/openclaw",
         "typescript": "^5.6.3",
         "vitest": "^4.1.3"
       }
     },
+    "../../../../../usr/lib/node_modules/openclaw": {
+      "dev": true
+    },
     "node_modules/@emnapi/core": {
       "version": "1.9.1",
       "resolved": "https://registry.npmjs.org/@emnapi/core/-/core-1.9.1.tgz",
@@ -914,6 +918,10 @@
       ],
       "license": "MIT"
     },
+    "node_modules/openclaw": {
+      "resolved": "../../../../../usr/lib/node_modules/openclaw",
+      "link": true
+    },
     "node_modules/pathe": {
       "version": "2.0.3",
       "resolved": "https://registry.npmjs.org/pathe/-/pathe-2.0.3.tgz",