Add explicit empty and error states to the error-handling view

[mikewheeleer]

Give error-handling clear empty and error states

Description

The error-handling view renders blank when there is no data or a load fails, leaving users without guidance. This issue adds distinct, accessible empty and error states.

Requirements and context

• Repository scope: StableRoute-Org/Stableroute-frontend only.
• Add an empty state and an error state (with retry) to error-handling, distinct from loading.
• Announce state changes for assistive tech; reuse the existing fetch-state model.
• Keep the retry keyboard-operable.

Suggested execution

• Fork the repo and create a branch
• git checkout -b feature/error-handling-01-states
• Implement changes
  • Write code in: the relevant module.
  • Write comprehensive tests in: cover the new behaviour and edge cases.
• Test and commit

Test and commit

• Run npm run lint, npm test, and npm run build.
• Cover edge cases: empty vs error vs loading exclusivity, retry re-fetches.
• Include the full test output in the PR description.

Example commit message

feat(error-handling): add empty and error states

Guidelines

• Minimum 95 percent test coverage for impacted modules.
• Clear, reviewer-focused documentation.
• Timeframe: 96 hours.

Community & contribution rewards

• 💬 Join the StableRoute community on Discord: https://discord.gg/37aCpusvx
• ⭐ This is a GrantFox OSS / Official Campaign task and may be rewarded. When your PR is merged you'll be prompted to rate the project — a 5-star rating is much appreciated.