Invoice Template: User-definable Accent Color

[clstaudt]

Problem

Invoice templates use hardcoded accent colors. Freelancers want invoices to match their corporate identity but cannot change the color scheme without editing HTML/CSS directly.

Proposed solution

Add a hex color setting to user preferences (e.g. #C8281E). Invoice templates pick up this value as their accent color instead of the hardcoded default.

Scope

• Settings: new accent_color field on User or in preferences
• Templates: replace hardcoded color values with a template variable, falling back to the current default when no custom color is set
• UI: hex color input in the settings/preferences screen for invoicing

This is independent of the broader AI template customization (#309) and can ship separately.