feat: add set-linking-limit support endpoint and CLI command

[Sneagan]

Summary

Adds a support operator endpoint and CLI command to set the per-order TLV2 credential batch limit (max_active_batches_tlv2_creds), enabling operators to increase the linked device cap for individual orders.

Backend:

• PATCH /v1/orders/{orderID}/credentials/batches/limit (supportMwr)
• SetMaxActiveBatches repo method on order_items
• SetLinkingLimit service method (validates paid + TLV2, runs in tx)
• SetLinkingLimitReq model type

CLI:

• bat-go skus set-linking-limit with --order-id or --email lookup, --max, optional --item-id, --private-key, and subscriptions service flags when using email; shows current limit/active count before confirming

Type of Change

• Product feature
• Bug fix
• Performance improvement
• Refactor
• Other

Tested Environments

• Development
• Staging
• Production

Before Requesting Review

• Does your code build cleanly without any errors or warnings?
• Have you used auto closing keywords?
• Have you added tests for new functionality?
• Have validated query efficiency for new database queries?
• Have documented new functionality in README or in comments?
• Have you squashed all intermediate commits?
• Is there a clear title that explains what the PR does?
• Have you used intuitive function, variable and other naming?
• Have you requested security and/or privacy review if needed
• Have you performed a self review of this PR?

Manual Test Plan