Enforce Lowercase Usernames

[Abdulazeem-code]

Description

Usernames should be case-insensitive to prevent impersonation.

Acceptance Criteria

• Usernames are converted to lowercase before saving
• Lookups force lowercase strings

Implementation Steps

1. Modify /register to apply .toLowerCase()
2. Modify /federation to do the same

Branching Instructions

Please create a branch from main following this naming convention:
feat/lowercase-usernames

[habdullhigh]

@habdullhigh has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

i would like to work on this issue maintaniner

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

[drips-wave]

Congratulations, @habdullhigh! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @habdullhigh: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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