refactor: remove device Pairing feature entirely (issue #645) (#650)

* refactor: remove device Pairing feature entirely (issue #645)

- Delete Pairing.kt model + pairing API endpoints (get/approve/revoke/clear)
- Delete PairingScreen/PairingViewModel + PairingCodeEntryScreen/ViewModel
- Remove NavKeys, ScreenRegistry drawer entry, Navigation.kt entry + Landing pairing button
- Remove pairing string resources (en + ko); keep connect_* config-parse strings
- Keep Telegram onboarding pairing_id flow (separate concept, per issue)
- Fix related doc comments + remaining test reference

* test: fix racy CONNECTED read in gated-mode WS test (issue #635 test)

testGatedMode_attemptsTicketFetchWithoutBareCookie asserted CONNECTED
immediately after the server-side onOpen latch fired, racing the client
handshake (WsListenerImpl sets CONNECTED on receipt of the 101). Await the
real status transition via connectionStatus.first{==CONNECTED} like the
other connect tests do. No product behavior changed.

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Co-authored-by: M57 <Hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/NavigationKeys.kt

@@ -25,10 +25,6 @@ import kotlinx.serialization.Serializable
 
 @Serializable data object AchievementsScreen : NavKey
 
-@Serializable data object PairingScreen : NavKey
-
-@Serializable data object PairingCodeEntryScreen : NavKey
-
 @Serializable data object ConfigScreen : NavKey
 
 @Serializable data object McpServersScreen : NavKey