RPI zero high CPU usage and overheating

I believe this is caused by hot climate (in the evening and morning my CPU drops to 15%, during midday it maxes out and overheats without adding some limiting as per https://github.com/getAlby/nostr-wallet-connect-next/pull/364/files)

Next steps I think could be:
- Can someone else simulate a hotter environment to confirm this issue? @reneaaron did you have this issue when you ran the RPI inside the case?
- Confirm LDK is the cause by testing RPI with a lightweight LNClient (like Cashu) or still happens with just NWC running on its own
- Profiling and performance improvements on the NWC side
- If the issue is on the LDK side, see what we can report to LDK so they can more easily fix it.

If we confirm the overheating issue, I would still propose adding an "Overheating" section at the bottom of the Alby Hub RPI guide as a **workaround** for people who run outside of Europe. Just saying "It works for me" is not a good solution...

No files, tests, or entry points are named. Start by reproducing the CPU and temperature increase in a hotter environment, then compare LDK, a lightweight LNClient such as Cashu, and NWC alone; done means identifying the responsible component and documenting an overheating workaround in the Raspberry Pi guide if confirmed.

Written by the indexing model from the issue text.