Fix offset validation and parsing in Angor routes

[miladsoft]

Pagination Offset Handling Improvements

Changes Made:

1. Modified offset handling in API endpoints to be more consistent with Blockcore Indexer:

   • Empty offset (?offset=) now defaults to 0
   • Explicit offset=0 (?offset=0) now defaults to 0
   • No offset parameter (?limit=10) defaults to 0

2. Fixed validation logic for offset parameter:

   • Now correctly validates empty string and "0" values
   • Error messages now show under correct "offset" key instead of "limit"
   • Improved type handling for undefined/null cases

3. Updated pagination header handling:

   • Modified setPaginationAndLinkHeaders to handle offset=0 cases consistently
   • First page link now includes explicit offset=0
   • Pagination-Offset header now always returns a numeric value

Testing Scenarios:

The following API calls now work consistently:

• ?limit=10 → offset=0
• ?limit=10&offset= → offset=0
• ?limit=10&offset=0 → offset=0
• ?limit=10&offset=10 → offset=10

Backwards Compatibility:

These changes maintain backwards compatibility while aligning behavior with Blockcore Indexer expectations.

Technical Details:

• Default offset value changed from undefined to 0
• Validation logic simplified to handle empty strings and "0" values uniformly
• Pagination links updated to always include explicit offset values

[dangershony]

Empty offset (?offset=) now defaults to 0

How do we deal with offset 0 then?
Normally offset 0 should return the first elements, and offset null should return he latest elements.
Instead of defaulting null to zero we need to allow null and treat null and latest items.

[Copilot]

Pull Request Overview

This PR improves offset handling and validation in Angor API endpoints to ensure consistent behavior with Blockcore Indexer expectations. Changes include:

• Updating offset parameter validation to treat empty and "0" values consistently
• Correcting error message keys from "limit" to "offset" where appropriate
• Adjusting pagination header links to always include an explicit offset value

[Copilot]

The added condition "queryOffset !== '0'" may cause an explicit offset value of '0' to bypass validation, which seems inconsistent with the intended default handling. Consider revisiting this condition to ensure that an explicit '0' is processed uniformly.

Suggested change

	if (typeof queryOffset === 'string' && queryOffset !== '' && queryOffset !== '0') {
	if (typeof queryOffset === 'string' && queryOffset !== '') {