feat(notifications): production-ready WebSocket gateway (TEC-2766)

- Add RedisIoAdapter (shared/infra) for multi-instance Socket.IO fan-out
  with graceful fallback to the in-memory IoAdapter when Redis is
  unreachable.
- Pin Socket.IO heartbeat (pingInterval/pingTimeout/connectTimeout)
  via env-tunable gateway options for reconnect stability.
- Expose Prometheus metrics on /notifications: goodgo_ws_connected_clients
  (Gauge) and goodgo_ws_messages_total (Counter) with namespace/event/
  direction labels. Wired through MetricsService and tracked across
  connect/disconnect + emits.
- Unit tests: RedisIoAdapter connect/fallback/close, new MetricsService
  WS helpers, and gateway metric increments/decrements on auth paths.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

pnpm-lock.yaml

@@ -147,6 +147,9 @@ importers:
       '@sentry/profiling-node':
         specifier: ^10.47.0
         version: 10.47.0
+      '@socket.io/redis-adapter':
+        specifier: ^8.3.0
+        version: 8.3.0(socket.io-adapter@2.5.6)
       '@willsoto/nestjs-prometheus':
         specifier: ^6.1.0
         version: 6.1.0(@nestjs/common@11.1.18(class-transformer@0.5.1)(class-validator@0.15.1)(reflect-metadata@0.2.2)(rxjs@7.8.2))(prom-client@15.1.3)
@@ -2869,6 +2872,12 @@ packages:
   '@socket.io/component-emitter@3.1.2':
     resolution: {integrity: sha512-9BCxFwvbGg/RsZK9tjXd8s4UcwR0MWeFQ1XEKIQVVvAGJyINdrqKMcTRyLoK8Rse1GjzLV9cwjWV1olXRWEXVA==}
 
+  '@socket.io/redis-adapter@8.3.0':
+    resolution: {integrity: sha512-ly0cra+48hDmChxmIpnESKrc94LjRL80TEmZVscuQ/WWkRP81nNj8W8cCGMqbI4L6NCuAaPRSzZF1a9GlAxxnA==}
+    engines: {node: '>=10.0.0'}
+    peerDependencies:
+      socket.io-adapter: ^2.5.4
+
   '@standard-schema/spec@1.1.0':
     resolution: {integrity: sha512-l2aFy5jALhniG5HgqrD6jXLi/rUWrKvqN/qJx6yoJsgKhblVd+iqqU4RCXavm/jPityDo5TCvKMnpjKnOriy0w==}
 
@@ -4222,6 +4231,15 @@ packages:
   dateformat@4.6.3:
     resolution: {integrity: sha512-2P0p0pFGzHS5EMnhdxQi7aJN+iMheud0UhG4dlE1DLAlvL8JHjJJTX/CSm4JXwV0Ka5nGk3zC5mcb5bUQUxxMA==}
 
+  debug@4.3.7:
+    resolution: {integrity: sha512-Er2nc/H7RrMXZBFCEim6TCmMk02Z8vLC2Rbi1KEBggpo0fS6l0S1nnapwmIi3yW/+GOJap1Krg4w0Hg80oCqgQ==}
+    engines: {node: '>=6.0'}
+    peerDependencies:
+      supports-color: '*'
+    peerDependenciesMeta:
+      supports-color:
+        optional: true
+
   debug@4.4.3:
     resolution: {integrity: sha512-RGwwWnwQvkVfavKVt22FGLw+xYSdzARwm0ru6DhTVA3umU5hZc28V3kO4stgYryrTlLpuvgI9GiijltAjNbcqA==}
     engines: {node: '>=6.0'}
@@ -5691,6 +5709,9 @@ packages:
     resolution: {integrity: sha512-6eZs5Ls3WtCisHWp9S2GUy8dqkpGi4BVSz3GaqiE6ezub0512ESztXUwUB6C6IKbQkY2Pnb/mD4WYojCRwcwLA==}
     engines: {node: '>=0.10.0'}
 
+  notepack.io@3.0.1:
+    resolution: {integrity: sha512-TKC/8zH5pXIAMVQio2TvVDTtPRX+DJPHDqjRbxogtFiByHyzKmy96RA0JtCQJ+WouyyL4A10xomQzgbUT+1jCg==}
+
   nypm@0.6.5:
     resolution: {integrity: sha512-K6AJy1GMVyfyMXRVB88700BJqNUkByijGJM8kEHpLdcAt+vSQAVfkWWHYzuRXHSY6xA2sNc5RjTj0p9rE2izVQ==}
     engines: {node: '>=18'}
@@ -6909,6 +6930,10 @@ packages:
   uid2@0.0.4:
     resolution: {integrity: sha512-IevTus0SbGwQzYh3+fRsAMTVVPOoIVufzacXcHPmdlle1jUpq7BRL+mw3dgeLanvGZdwwbWhRV6XrcFNdBmjWA==}
 
+  uid2@1.0.0:
+    resolution: {integrity: sha512-+I6aJUv63YAcY9n4mQreLUt0d4lvwkkopDNmpomkAUz0fAkEMV9pRWxN0EjhW1YfRhcuyHg2v3mwddCDW1+LFQ==}
+    engines: {node: '>= 4.0.0'}
+
   uid@2.0.2:
     resolution: {integrity: sha512-u3xV3X7uzvi5b1MncmZo3i2Aw222Zk1keqLA1YkHldREkAhAqi65wuPfe7lHx8H/Wzy+8CE7S7uS3jekIM5s8g==}
     engines: {node: '>=8'}
@@ -10174,6 +10199,15 @@ snapshots:
 
   '@socket.io/component-emitter@3.1.2': {}
 
+  '@socket.io/redis-adapter@8.3.0(socket.io-adapter@2.5.6)':
+    dependencies:
+      debug: 4.3.7
+      notepack.io: 3.0.1
+      socket.io-adapter: 2.5.6
+      uid2: 1.0.0
+    transitivePeerDependencies:
+      - supports-color
+
   '@standard-schema/spec@1.1.0': {}
 
   '@standard-schema/utils@0.3.0': {}
@@ -11548,6 +11582,10 @@ snapshots:
 
   dateformat@4.6.3: {}
 
+  debug@4.3.7:
+    dependencies:
+      ms: 2.1.3
+
   debug@4.4.3:
     dependencies:
       ms: 2.1.3
@@ -13190,6 +13228,8 @@ snapshots:
 
   normalize-path@3.0.0: {}
 
+  notepack.io@3.0.1: {}
+
   nypm@0.6.5:
     dependencies:
       citty: 0.2.2
@@ -14609,6 +14649,8 @@ snapshots:
 
   uid2@0.0.4: {}
 
+  uid2@1.0.0: {}
+
   uid@2.0.2:
     dependencies:
       '@lukeed/csprng': 1.1.0