`end_campaign` and automatic deadline-based ending

[ayshadogo]

User Story:
As a campaign creator, I want to close my campaign early, and I want the contract to enforce automatic ending at the deadline, so that fundraising windows are respected without manual admin intervention.

Acceptance Criteria:

• fn end_campaign(env): creator-only, sets status Ended, panics if already Ended/Cancelled, emits campaign_ended, does not block a subsequent final milestone release
• Public fn update_status(env) callable by anyone, transitions an expired-but-still-Active campaign to Ended and emits the event — explain why this needs to be callable by any address rather than just the creator
• Test: campaign past deadline still Active until update_status (or a donation attempt) triggers the transition

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[Hollujay]

I would like to work on this issue because I will get it done efficiently @ayshadogo

[A6dulmalik]

I’d like to work on this issue. I can implement the campaign-ending logic, deadline-based status transition, event emissions, and the associated tests.

[grantfox-oss]

🦊 GrantFox — @A6dulmalik has been assigned to this issue as part of the Third Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #35)
2. Your PR will be reviewed by the Dfunder maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Third Campaign campaign!

@A6dulmalik's PR #57 was approved and merged by @ayshadogo.

🏆 @A6dulmalik: You earned 40 FoxPoints for this contribution! Your current tier: Builder (1,305 total points). Track your full progress on GrantFox.

👏 Great work, @A6dulmalik! Keep contributing to Dfunder.