ci: include fork changes in mirror linux build release notes

[TonybynMp4]

What Changed

Updated the mirror Linux build workflow to include this fork's own commits in the generated release notes. The workflow now:

• Fetches full git history (without blobs) to access commit metadata and references
• Identifies the previous release on the same channel (stable/nightly/preview/prerelease)
• Extracts first-parent non-merge commits since that previous release (this fork's own changes)
• Inserts those changes into release notes before upstream's "New Contributors" section
• Records the mirror-main commit SHA as a comment for future releases to reference

Why

Users running the mirror Linux builds now see what fork-specific changes were included in each release. Since each fork change is announced once per channel, users get accurate release notes without duplicate entries across channels. The commit reference allows future releases to calculate the correct range of fork changes.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

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Note: This diff includes additional changes to mobile components, server orchestration, and web UI that should be separated into focused PRs per the contribution guidelines.