refactor: Use GitHub forks for Swift 6.3 compatibility

Update all local path dependencies to use GitHub forks:
- doozMen/GRDB.swift (master) - synced with upstream v7.9.0
- doozMen/swift-sharing (main) - Swift 6.3 fixes for swift-perception
- doozMen/swift-structured-queries (main) - Swift 6.3 compiler crash guards

All CloudKit code guarded with `!compiler(>=6.3)` to avoid compiler crashes.
Tested successfully with Swift 6.3-dev snapshot.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Stijn Willems