refactor: Deduplicate battery drawing code and fix Lyra charging indicator (#1437)

## Summary

**What is the goal of this PR?**

Following up on #1427:
- Extracted shared battery drawing logic, including lightning bolt, to
reduce duplication.
- In Lyra with segmented battery the lightning bolt was hard to see, so
when charging Lyra now uses a solid battery fill.

---

### AI Usage

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src/components/themes/BaseTheme.h

@@ -142,4 +142,9 @@ class BaseTheme {
   virtual void drawTextField(const GfxRenderer& renderer, Rect rect, const int textWidth) const;
   virtual void drawKeyboardKey(const GfxRenderer& renderer, Rect rect, const char* label, const bool isSelected) const;
   virtual bool showsFileIcons() const { return false; }
+
+  // Shared constants and helpers for battery drawing (used by all themes)
+  static constexpr int batteryPercentSpacing = 4;
+  static void drawBatteryOutline(const GfxRenderer& renderer, int x, int y, int battWidth, int rectHeight);
+  static void drawBatteryLightningBolt(const GfxRenderer& renderer, int boltX, int boltY);
 };