[Feature] Add in-app settings search functionality #240

As MonoGram grows with more customization options (themes, gestures, chats, data, privacy, etc.), it becomes harder to quickly find a specific setting. Users currently have to manually browse through multiple categories (e.g., "Appearance", "Notifications", "Privacy") to locate a single toggle or preference.

Proposal

Add a search button at the top of the main Settings screen (like in main screen) that allows users to filter settings by keywords. For example:

• Typing "font" should show options related to text size or font style.
• Typing "backup" or "cloud" should highlight relevant data/chat backup settings.
• Typing "biometric" should point directly to the security/lock option.

The ideal implementation would:

1. Dynamically scan all available settings screens and preference keys.
2. Display a list of matching results with their full navigation path (e.g., Settings → Privacy → Passcode Lock).
3. Navigate the user directly to the highlighted setting when tapped.

Additional context

• This is a standard feature in many modern apps (Telegram X, Signal, and even the official Telegram client).
• It would greatly improve UX for both new and power users, aligning with MonoGram's goal of being a "fast and elegant" client.