Clean Swift vstyle violations

[yvette-carlisle]

Summary

• remove Swift unary logical negation patterns that trip the Swift vstyle runtime rule
• replace remaining Swift force unwraps in the app server bridge and icon renderer with guarded paths
• add required numeric separators for large Swift integer literals

Validation

• vstyle curate --language swift --workspace
• swiftc -typecheck scripts/assets/render_decodex_app_icons.swift
• swift build (apps/decodex-app)
• cargo make test-decodex-app-stage
• cargo make check-vstyle-rust
• git diff --check