[2026 Testing] Create lighthouse performance budgets for mobile and desktop

[Nanle-code]

Objective

Define and enforce Lighthouse budgets for LCP, CLS, and TBT on key routes.

Target area

lhci and performance docs

Acceptance criteria

• The objective is implemented with clear handling for invalid input, unsupported environments, and failure paths.
• Automated tests cover the primary flow, at least one boundary case, and at least one failure case.
• User-facing documentation or developer guidance is updated, including compatibility, security, or migration notes where applicable.
• Pull requests that address this issue must keep the branch free of merge conflicts with the target branch.
• All continuous integration checks must pass before the pull request may be merged; failing, pending, or skipped required checks are not acceptable for merge.

Pull request requirements

• All continuous integration checks must pass before a pull request may be merged.
• The branch must be free of merge conflicts with the target branch at the time of merge.
• Do not request merge with failing workflows, skipped required checks, or unresolved conflicts.

[0darkside0rbit-star]

@0darkside0rbit-star has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I would like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @0darkside0rbit-star to this issue.

[Jessicaayegh]

@Jessicaayegh has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer! I’d love to work on this issue if it’s still available. I have a good understanding of the requirements and would be happy to implement the solution. Thanks for considering my request!

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Jessicaayegh to this issue.