docs: fix dead and corrupted resource links (#10400)

Fixes 20 resource links across roadmaps:
- Repair corrupted/truncated URLs (trailing junk, missing slashes,
  wrong slugs): vscode, goperf, laminar, pkg.go.dev/std, pandas query,
  Scala Days YouTube, CircleCI discuss, JUnit, PostgreSQL DBA roadmap
- Update moved official docs: Elixir processes guide (hexdocs),
  Kotlin Flow, Cloudflare Calls, Infura, TestNG
- Remove dead daily.dev tag feed links (pages no longer exist)
- Unlink the username.github.io placeholder in the GitHub Pages intro

All replacement URLs verified to resolve (HTTP 200).

Co-authored-by: Weijian He <230282609+Madin-H23@users.noreply.github.com>

roadmaps/java/content/junit@hY1-sEpTmpaj1PregdkFf.md

@@ -4,7 +4,7 @@ JUnit is a widely-used open-source testing framework for the Java programming la
 
 Visit the following resources to learn more:
 
-- [@official@JUnit](https://junit.org/junit5)
+- [@official@JUnit](https://junit.org/junit5/)
 - [@official@JUnit Documentation](https://junit.org/junit5/docs/current/user-guide/)
 - [@article@JUnit tutorial](https://www.guru99.com/junit-tutorial.html)
 - [@article@Basic JUnit tutorial](https://www.baeldung.com/junit-5)

roadmaps/java/content/testng@XU2C8bF9ICej8LS7ZGTTv.md

@@ -5,5 +5,5 @@ TestNG is a testing framework inspired from JUnit and NUnit but introducing some
 Visit the following resources to learn more:
 
 - [@official@Testng](https://testng.org)
-- [@official@Testng Documentation](https://testng.org/doc/documentation-main.html)
+- [@official@Testng Documentation](https://testng.org/)
 - [@article@Testng tutorial](https://www.guru99.com/all-about-testng-and-selenium.html)