Recognise wrong QR code type in every scanner

When a scanner is shown a QR code of a different kind than it expects, it
now tells the user what they actually scanned and where to use it, instead
of a generic "invalid" message.

Link recognition is done in the core: a new chat_check_link export
classifies a scanned string using the same decoders the views use to
process the links (connection link, server address, migration file link,
desktop address, security code), returning a typed result. Each scanner
calls checkLink first; the expected type proceeds to that scanner's normal
success path, a recognised-but-wrong type shows a shared wrong-type alert
saying what it is and where to use it, and an unrecognised string falls
back to that scanner's own contextual error. Mirrored on Android, desktop
and iOS.

Note: the iOS Swift was written without an Xcode toolchain and is not yet
compiled — needs a Mac/CI build to verify.

apps/multiplatform/spec/database.md

@@ -143,7 +143,7 @@ external fun chatMigrateInit(dbPath: String, dbKey: String, confirm: String): Ar
 
 ### Migration Flow in `initChatController`
 
-The full initialization sequence is in [Core.kt#L62](../common/src/commonMain/kotlin/chat/simplex/common/platform/Core.kt#L62):
+The full initialization sequence is in [Core.kt#L63](../common/src/commonMain/kotlin/chat/simplex/common/platform/Core.kt#L63):
 
 1. Obtain the DB encryption key from `DatabaseUtils.useDatabaseKey()`.
 2. Determine the confirmation mode (default: `YesUp`; developer mode with confirm upgrades: `Error`).