Rework charge sensor device styling

[kiro-agent]

This pull request was created by @kiro-agent on behalf of @VanOschB 👻

Comment with /kiro fix to address specific feedback or /kiro all to address everything.
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Summary

• Restyles the charge sensor and double-dot device to closely match the supplied gray-reservoir reference.
• Uses smaller separated blue islands with black center markers and extended blue tunnel barriers.
• Preserves the capacitive coupling and uniform Coulomb-blockade peak callout while keeping all dot interiors text-free.

Verification

• Visually inspected the 1016×861 PNG against the attached reference.
• Confirmed four gray reservoirs, three blue islands, three black center markers, and a 21 px lower-dot gap.
• Confirmed no charge-sensor or quantum-dot labels remain inside the device.
• Confirmed PNG dimensions and matching SVG viewBox.

Limitations

• None.