[devmobasa]

Standardize Rust style across the core app and GTK configurator, and add checks to keep future changes consistent.

• Enable workspace Clippy rules and document the shared conventions.
• Normalize imports and add a repository guard that enforces one module per use statement.
• Improve borrowing, panic documentation, assertion messages, and unsafe-code explanations.
• Replace poisoned-lock recovery with explicit failure or safe fallbacks.
• Keep shared test resources releasable after a panic.
• Wait for GTK popup layout to settle before recording reference pixels in capture tests.