fix: Replace all hard-coded port 6989 with SERVER_PORT env var

[eduardomozart]

📋 Description

Hard-coded port 6989 was scattered across source and config files, preventing SERVER_PORT from being respected end-to-end.

Changes

• server/index.js — already used process.env.SERVER_PORT || 6989 (no change needed)
• client/vite.config.js — dev proxy target now derives port from SERVER_PORT:

  target: `http://localhost:${process.env.SERVER_PORT || 6989}`

• server/openapi.js — development API server URL in the OpenAPI spec:

  { url: `http://localhost:${process.env.SERVER_PORT || 6989}/api`, ... }

• landing/src/pages/Install/Install.jsx — access URL hint uses Vite's build-time env convention:

  <code>http://localhost:{import.meta.env.VITE_SERVER_PORT || 6989}</code>

• Dockerfile — retains EXPOSE 6989 as a static documentation hint; actual runtime port is controlled via SERVER_PORT

🚀 Changes made to ...

• 🔧 Server
• 🖥️ Client
• 📚 Documentation
• 🔄 Other: ___

✅ Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have looked for similar pull requests in the repository and found none
• This pull request does not contain translations (translations are managed through Crowdin)

🔗 Related Issues

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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