fix: validate lock positions, min lock period, and typed errors

[umuewu]

Description

Fixes position stake validation, minimum lock period validation, historical credit rate events, and typed errors for batch whitelist operations.

Closes #228
Closes #227
Closes #226
Closes #225

Changes proposed

What were you told to do?

Resolve assigned issues #228, #227, #226, #225.

What did I do?

Farming Pool & Factory Enhancements

• Enforced total position stake check against minimum stake in lock_assets
• Added minimum lock period validation in factory create_pool
• Updated batch whitelist operations to return typed error BatchTooLarge
• Included ledger sequence in rate_set events

Check List

• My code follows the code style of this project.
• This PR does not contain plagiarized content.
• The title and description of the PR is clear and explains the approach.
• I am making a pull request against the main branch (left side).
• My commit messages styles matches our requested structure.
• The implementation was reviewed and confirmed to work as intended.
• I am only making changes to files I was requested to.

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