feat: implement Epic/Standard content filter toggle

[Franc3s-bot]

Closes #65.

Overview

This PR implements the requested filtering between Standard and Epic game data. It adds a global toggle in the frontend and enforces the filter at the backend service layer.

Technical Changes

• Backend: Added include_epic parameter to get_meta_snapshot in backend/app/api/meta.py. Tournaments are now filtered using Tournament.format.
• Frontend State: Added includeEpic to the filters store (frontend/src/lib/stores/filters.svelte.ps1).
• UI: Implemented a mode toggle in ShipChassisFilter.svelte with custom X-Wing iconography and terminal styling.
• Proxy: Updated api/meta-snapshot proxy to forward parameters to the internal backend.
• Pages: Updated Dashboard, Ships, and Lists pages to respect the filter and ensure URL persistence.

Verification

• API returns filtered data based on the include_epic flag.
• UI reactively updates across all browser pages.
• URL parameters are correctly synchronized.