Implement Transaction Tagging and Categorization

[Olowodarey]

Description:
Allow users to tag and categorize their transactions for better financial tracking and reporting. Auto-categorize transactions using ML.

Acceptance Criteria:

• Add tags and category fields to Transaction entity
• POST /transactions/:id/tag endpoint
• GET /transactions/categories for category list
• Auto-categorization service using transaction metadata
• Bulk tagging API
• Category-based filtering in transaction history
• Export transactions by category

[MerlinTheWhiz]

@MerlinTheWhiz has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I'd love to work on this please

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

[drips-wave]

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

🧑‍💻 @MerlinTheWhiz: 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.

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[drips-wave]

This issue has been completed by @MerlinTheWhiz as part of the Stellar Wave Program's 3rd Wave 🥳

😎 @MerlinTheWhiz: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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