nodejs: lazy per-backend libsimplex download (#7543)

* ci: drop dlltool from nodejs libs release

* nodejs: download libsimplex into the user cache

* nodejs: load libsimplex at runtime per backend

* support bot: select db backend with --db

* python: match backend switch error text

* nodejs: download prebuilt add-on at runtime

* ci: build nodejs add-on for libs release

* calculator bot: load libs and add-on in image

* support bot: document add-on override

* nodejs: keep worker test output free of colors

* nodejs: verify sha-256 of downloaded assets

* python: pin core libs release with sha-256

* ci: add packages release script

* ci: release nodejs add-on and open release PR

* ci: publish packages after release PR

* nodejs: keep npm from building the add-on

* calculator bot: build the add-on in the image

* ci: merge package release workflows

* ci: open release PR when publishing fails

* ci: build the add-on with node-addon-api only

* ci: skip publishing in a called packages workflow

* ci: update package release actions to Node 24

* nodejs: fix receive test timeout

* ci: test packages on pull requests

* nodejs: reuse the database in the close stress test

* ci: keep failed package tests from hanging

* ci: skip preset server tests

* ci: plan package builds from the changes

* ci: test packages with a given libsimplex

* ci: test packages with libsimplex of core changes

packages/simplex-chat-nodejs/docs/Namespace.core.md

@@ -32,6 +32,7 @@ You are unlikely to ever need to use this module directly.
 
 ## Type Aliases
 
+- [Backend](core.TypeAlias.Backend.md)
 - [DBMigrationError](core.TypeAlias.DBMigrationError.md)
 - [MigrationError](core.TypeAlias.MigrationError.md)
 - [MTRError](core.TypeAlias.MTRError.md)
@@ -46,3 +47,4 @@ You are unlikely to ever need to use this module directly.
 - [chatRecvMsgWait](core.Function.chatRecvMsgWait.md)
 - [chatSendCmd](core.Function.chatSendCmd.md)
 - [chatWriteFile](core.Function.chatWriteFile.md)
+- [loadLibrary](core.Function.loadLibrary.md)