Polish Notifications Permissions Request

[ovitrif]

Some UX improvements could be addressed in follow-up PRs:

• Request permission once even without LN balance because of CJIT and channel opening, or at least in these specific flows
• Make the FG service optional, since it became less vital after ldk-node caching improvements
  • Could be an option in background payments settings. Would need some design work

Originally posted by @jvsena42 in #1004 (comment)

[jvsena42]

Some more context: The Foreground service keeps the Lighting node running in background and for this the system demands a persistent notification.

It was implemented because of some UX issues caused by the node stop/start timing every time the app is backgrounded. Because of this, wallets with many HTLCs had to wait like 10 seconds for every wallet resume

After the caching improvements, this waiting time reduced drastically. IMO it is good enough already to make the FG service optional and disabled as default

It also helps on receiving reliability, because the google notification delivery is not 100% reliable, so the app may not wake for LN operations like receive, open channel, coop-close

[jvsena42]

https://www.figma.com/design/ltqvnKiejWj0JQiqtDf2JJ?node-id=40364-135743&m=dev#1808759889

Waiting for design

[jvsena42]

Users feedback:

https://synonymworkspace.slack.com/archives/C07BJ7DNPCG/p1781513006019249

https://synonymworkspace.slack.com/archives/C07BJ7DNPCG/p1781757774287639