WIP - Issue5164 - open backend sources (2fa, multisig, invoices)

[shendel]

Checklist

• I have read the CONTRIBUTING guide
• Good naming (as clear and simple as possible)
• Correct behavior if external API endpoints are down, return 404, 504 (or no answer), 401 errors (ddos simulation)
• I tested desktop/mobile resolution
• I tested light/dark theme
• I tested different languages
• I checked the functionality once again (AFFECT MONEY)
• I checked the work on the Testnet
• I checked the work on the Mainnet
• I checked the work in the plugin
• I checked the PR once again

Tests

Please start auto tests as follows:

• add a label swap test to start swap tests
• add a label withdraw test to start withdraw tests

You can skip these tests if you completely sure that your changes aren't related to this functional

Original issue

#5164

Video / screenshot proof

[cloudflare-pages]

Deploying with    Cloudflare Pages

Latest commit:	e071aa3
Status:	✅  Deploy successful!
Preview URL:	https://4c8f0e2e.multicurrencywallet-btg.pages.dev
Branch Preview URL:	https://issue5164.multicurrencywallet-btg.pages.dev

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