add tradeoff document for backplane connector standard

[FerretCode]

Summary

What changed and why:

Added a new tradeoff report that considers different backplane connector standards and settles on one based on a set of decision criteria.

Related issue/ticket (if any):

#86

Type of Change

• Hardware - schematic
• Hardware - layout
• Firmware - new service/module
• Firmware - refactor of existing service/module
• Documentation only
• Other:

Affected subsystem(s):

Backplane

Requirements Traceability

• This change is covered by an existing requirement in the subsystem's information doc
• This change requires a new or updated requirement in the information doc (link/describe below)
• This change requires an update to the CDS-compliance checklist (see the Preliminary Hardware Design Guidelines)

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ATP / Bring-Up Impact

• This change affects a board/unit that already has a released ATP: ATP updated or flagged for update
• This change was verified via bring-up/test procedure (attach results or link)
• No impact to existing ATP

Deviations

List any deviation from the design guideline docs introduced by this PR, with justification. Leave blank if none.

Guideline doc	Deviation	Justification	Approved by

Reviewer Sign-off

• I reviewed this PR against the relevant checklist section(s) above, not just the diff
• Any checked-but-not-actually-verified items were flagged and discussed with the author
• No open anomalies/deviations without an approver

[github-actions]

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