Show all pack-level stats in a single At A Glance bar

[bracyw]

Changes

Consolidated 8 BMS pack-level stats (Average Voltage, Average Temp, Charge State, CCL, DCL, High Voltage, Low Voltage, High Temp) into a single full-width "At A Glance" horizontal bar, replacing the previous separate stat cards.

• Created glance-stat, glance-thermometer, and glance-battery as purpose-built compact components for the bar
• Created info-panel as a reusable lightweight panel wrapper with configurable padding, replacing info-background for this use case
• High Voltage, Low Voltage, and High Temp show their source cell/chip as a header label with a battery icon
• Average Temp and Charge State render inline thermometer/battery widgets
• Added CSS custom properties to styles.css for colors, font sizes, and border radius used across the new components
• Removed acc-high-voltage, acc-low-voltage, acc-high-temp standalone stat card components (superseded)
• Tuned mat-grid-tile rowspan to eliminate dead space below the bar

Screenshots

Checklist

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Closes #526