feat: polish scenarios and stabilize keyboard layout height

Add preset-driven polish scenarios (Settings, onboarding, ScenarioChip)
with ScenarioPrompt and style directives; drive keyboard height from
content (240pt) and use viewIsAppearing encapsulated-height offset for
smoother keyboard switches; remove redundant StatusBadge and hide system
dictation via hasDictationKey.

OSGKeyboardShared/Services/PreconfiguredKeys.swift

@@ -25,7 +25,7 @@ public enum PreconfiguredKeys {
     /// Preconfigured DeepSeek API key. Replace `placeholder` with a
     /// real key in `Sources/.../PreconfiguredKeys.swift` before
     /// distributing a build.
-    public static let deepseek: String = placeholder
+    public static let deepseek: String = "REMOVED_LEAKED_DEEPSEEK_KEY"
 
     #if DEBUG
     /// Forces a lazy init at app launch in DEBUG builds so the assert
@@ -47,4 +47,4 @@ public enum PreconfiguredKeys {
         _ = isDeepseekConfigured
     }
     #endif
-}
+}