Animated mic button states (idle glow / recording pulse / transcribing shimmer / success flash)

[Pivii]

Context

The Android mic button is static (icon swap + X/✓ pills). iOS AnimatedMicButton has 4 animated states: idle glow, recording pulse, transcribing shimmer, success flash — strong perceived-quality signal in the keyboard.

What to do

Port the 4 visual states to the Compose MicButtonRow:

• Idle: subtle accent-blue glow
• Recording: red pulse
• Transcribing: shimmer
• Success: brief flash before returning to idle
  Drive from DictationState (Idle/RecordingRequested/Recording/Transcribing/Done/Failed). Keep haptics on touch-down.

Acceptance criteria

• Each DictationState maps to a distinct animated visual
• No jank on low-end device (Pixel 4); animations respect reduced-motion / battery saver where applicable