fix(import): make rollback all-or-nothing at the queue level

[Priyanshu1-62]

Description

Summary:

This addresses the import atomicity issue: "validate all rows up front" and "roll back atomically."

• validator.ts: No code changes. runValidationPipeline already iterates every row regardless of earlier row failures and returns full succeeded/failed/records results, the "validate all rows up front" behavior already exists as written.
• rollback.ts: Updated so rollback is all-or-nothing at the queue level. Previously, rollback() unconditionally cleared all registered actions after attempting them, even when some failed, silently discarding the fact that cleanup was incomplete. Now the queue only clears on full success; failed actions remain registered so a retry only re-attempts what didn't complete.

Implementation Details:

• RollbackResult gains a complete: boolean field, true only when every action succeeded and the queue is now empty.
• rollback() no longer unconditionally zeroes actions. On partial failure, failed actions are re-queued in their original relative order instead of being discarded.
• size now honestly reflects incomplete rollback state (non-zero after a partial failure) instead of always reading 0 post-rollback.
• register(), clear(), and execution order (reverse/LIFO) are unchanged.

Related Issue

Closes #1180

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Checklist

• Code follows project style guidelines
• Self-review completed
• No console errors
• Uses Lucide icons consistently
• Responsive design implemented
• Starknet best practices followed

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