fix(jira): use Jira created timestamp and inner join for changelog convertor (#8834)

[bujjibabukatta]

Fixes #8834

Problem

Two bugs in ConvertIssueChangelogs cause changelog items to be silently
dropped from the domain layer:

1. Incremental filter (line 107) filters on _tool_jira_issue_changelog_items.created_at
   which is the DevLake internal DB insertion timestamp (NoPKModel.CreatedAt),
   not the Jira changelog's Created date. Changelog items inserted in the same
   batch can fall on either side of the since cutoff, silently dropping items
   from that batch on the next incremental run.

2. LEFT JOIN on _tool_jira_board_issues with board_id filter in WHERE clause
   is a LEFT JOIN used as INNER JOIN. Any issue not in board_issues produces a
   NULL board_id row which the WHERE silently drops. Moving board_id into the
   JOIN condition as INNER JOIN makes intent explicit and eliminates duplicate
   rows when an issue belongs to multiple boards.

Changes

• backend/plugins/jira/tasks/issue_changelog_convertor.go:
  • Change LEFT JOIN _tool_jira_board_issues to INNER JOIN with board_id = ?
    in the join condition instead of WHERE
  • Change incremental filter from _tool_jira_issue_changelog_items.created_at
    to _tool_jira_issue_changelogs.created

[bujjibabukatta]

Hi @klesh could you please approve pull request?