Add missing privacy usage description strings (Mac App Store)

Part of: #9941

## Problem

The main app's `Info.plist` may lack privacy usage description keys for resources accessed at runtime. Apple rejects any app that accesses a protected resource without a corresponding usage description string.

Keys to audit and add if applicable:

| Resource | Key |
|---|---|
| Local network / mDNS discovery | `NSLocalNetworkUsageDescription` + `NSBonjourServiceTypes` |
| Contacts (share-to-contacts feature) | `NSContactsUsageDescription` |

## Required change

Audit runtime resource access and add the appropriate `*UsageDescription` strings to the main app `Info.plist` template. Strings will be reviewed by Apple and must be user-facing and accurate.