Feature request: Add Dark Theme support (Auto/System/Dark)

### Is your feature request related to a problem? Please describe.
Currently, IPFS Desktop lacks visual customization options for low-light environments. The bright interface can be straining for users who work at night or prefer darker aesthetics, and it stands out inconsistently against modern operating systems that are set to "Dark Mode".

### Describe the solution you'd like
**The Request:** Add a native Dark Theme option.

**Suggested behavior:**
Add a setting under *Preferences > Appearance* with the following options:
* **Auto:** Respects the system-wide preference (OS theme).
* **Light:** Forces the classic light theme.
* **Dark:** Forces the new dark theme.

**Why this is important:**
* **Accessibility & Health:** Reduces eye strain for users working in low-light conditions.
* **Modern Standards:** Dark mode is a standard requirement for modern applications on Windows 10/11, macOS, and Linux.
* **Aesthetics:** Integrates better with the user's desktop environment.

### Alternatives considered
* Using third-party tools/extensions to invert colors (suboptimal and buggy).