[50 MRG] Firmware: deep sleep + battery reporting #9

50 MRG

Low-power farm node mode.

Acceptance

• Config flags + docs

Claim

1. Star https://github.com/mergeos-bounties/HIRI and https://github.com/mergeos-bounties/mergeos
2. Comment: I claim this bounty
3. MergeOS Claim #1 with issue link
4. PR to HIRI with Fixes #<n>

Policy: docs/BOUNTY.md