fix: Hide "Issues connecting?" on Splash Screen if no URL set

[Taarek]

Summary

• What changed: Added a way to configure status page URL and incident history URL, so you can reuse the component showing up when the connection process takes longer than usual on the splash screen, otherwise it's hidden.
• Why it is correct: This seemed to correct approach, instead of outright hiding it for all self-hosted instances
• Risk: This does introduce a breaking change for the official instance, but @hampus-fluxer have been made aware of it.

Verification

• Tests run: Biome and TS linting
• Manual checks:
• Screenshots or recordings:

Checklist

• I understand every change in this PR.
• I can explain what it does and why it is correct.
• I disclosed any LLM coding help below.

LLM Disclosure

• Had some help from Codex to make sure I did not miss some file to apply these changes to, instance configs resided in a lot more files than I initially thought when I started this PR.

closes #1259

[Jiralite]

• These need to be added to packages/config/src/config_loader/EnvironmentOverrides.ts
• fluxer_app/src/features/user/state/StatusPage.ts polls hard-coded ExternalUrls.SERVICE_STATUS still. It will also fetch maintenance from that hard-coded value too. For correctness, let's swap them to the defined RuntimeConfig.statusPageUrl value. This is mainly a code correctness issue for the main instance where it will pointlessly poll if the main instance does not have one set
• Please run the OpenAPI script generators. When schemas are updated, the JSON files need to be updated too (pnpm run openapi:generate)