Add player names: settings persistence, replication, screen-space nameplates

- GameSettings: playerName field persisted in Settings.json
- NetworkPlayerSetup: owner-written DisplayName NetworkVariable
  (seeded from settings on spawn, sanitized/truncated, live rename push)
- PlayerNameField: binds the session panel name input to settings
- PlayerNameplates: screen-space overlay labels above players with
  distance-based font scaling (clamped min/max), pooling, FP self-hide

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/Scripts/Network/UI/PlayerNameField.cs.meta

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