feat: Integrate BTC Map module for merchant discovery and listing

[JordyPirata]

This PR integrates BTC Map directly into the Ambrosia POS dashboard as a dedicated module. This feature allows merchants to view a global map of businesses that accept Bitcoin and provides a seamless interface for them to list their own business.

Key Changes

• New Module: Added src/modules/btcmap/MapEmbed.jsx which embeds the BTC Map interface using an iframe.
• Dual Mode: Implemented a toggle allowing users to switch between the standard "Map View" (for discovery) and "Add Location" mode (to streamline the listing process).
• Integration: Wrapped within the StoreLayout to maintain consistent navigation and UI/UX.
• Localization: Added translation keys (btcmap) to support internationalization.

Justification

• Ecosystem Growth: By making it easier for merchants to see the growing network of Bitcoin-accepting businesses, we reinforce the value of their decision to accept Bitcoin.
• Merchant Visibility: The "Add Location" integration lowers the friction for merchants to list their own business, directly increasing their visibility to customers who use BTC Map to find places to spend sats.
• Unified Workflow: Keeps the merchant within the POS environment, avoiding the need to navigate away to external browser tabs for these ecosystem-related tasks.

Risks & Considerations

• External Dependency: This feature relies entirely on the availability and stability of btcmap.org. If their service experiences downtime or API changes, this module may break.
• Iframe Security: Embedding external content always introduces a potential attack surface. We are using the sandbox="allow-scripts allow-same-origin allow-forms" attribute to restrict the iframe's capabilities, but we must trust the upstream source (btcmap.org) to remain secure.
• Privacy: Loading the map connects the client directly to BTC Map's servers, which exposes the user's IP address and potential geolocation data (if granted) to the third-party service.
• Performance: Map applications can be resource-intensive. While loaded in an iframe, it may still impact the memory usage of the POS client, especially on lower-end hardware.