🔒 Fix security vulnerabilities in dependencies

- next: 15.2.4 → 15.2.6+ (critical RCE fix)
- mermaid: 11.7.0 → 11.10.0+ (XSS fixes)
- eslint: 9.23.0 → 9.39.1 (plugin-kit ReDoS fix)
- @marp-team/marp-core: 4.0.1 → 4.2.0 (js-yaml fix)
- Add pnpm overrides for transitive dependencies

Author: yceffort

package.json

@@ -55,7 +55,7 @@
     ],
     "overrides": {
       "markdown-it-mermaid>mermaid": "^11.10.0",
-      "js-yaml": "^4.1.1",
+      "@marp-team/marpit>js-yaml": "^4.1.1",
       "brace-expansion@>=1.0.0 <1.1.12": "^1.1.12",
       "brace-expansion@>=2.0.0 <2.0.2": "^2.0.2",
       "@eslint/plugin-kit": "^0.3.4",