docs: fix blockchain RPC port references and dead links

- Update blockchain RPC port from 8081 to 9080 across infrastructure docs
- Fix confidential transactions documentation cross-references
- Standardize "Blockchain Node RPC" naming in services table

.github/workflows/markdown-link-check.yml

@@ -0,0 +1,32 @@
+name: Markdown Link Check
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'docs/**'
+      - '**.md'
+  pull_request:
+    branches: [main]
+    paths:
+      - 'docs/**'
+      - '**.md'
+
+jobs:
+  link-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Run lychee link checker
+        uses: lycheeverse/lychee-action@v1
+        with:
+          args: --verbose --no-progress --exclude 'mailto:*' --exclude 'https://dashboard.aitbc.io/*' --exclude 'https://aitbc.bubuit.net/admin/*' --exclude 'https://aitbc.bubuit.net/api/*' --exclude 'https://docs.aitbc.bubuit.net/*' --exclude 'https://aitbc.io/*' --exclude 'http://localhost:*' --exclude 'http://aitbc.keisanki.net:*' --exclude 'https://docs.aitbc.net/*' --exclude-file .lycheeignore 'docs/**/*.md' '**.md'
+          fail: true
+
+      - name: Upload link check results
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: link-check-results
+          path: lychee/out.md