feat: add application attribution

[kev1n77]

Summary

• add versioned application attribution to CaptureEnvelope and Capture Policy
• derive explicit client labels, User-Agent matches, or honest low-confidence capture-mode fallbacks
• strip x-codeischeap-client before persistence and upstream forwarding
• expose attribution source/confidence in desktop list, Inspector, Raw evidence, and exports
• update CAP-007 progress while leaving PID and certificate-pinning diagnostics outstanding

Verification

• cargo fmt --all -- --check
• cargo test --workspace --all-targets
• cargo clippy --workspace --all-targets -- -D warnings
• cargo fmt --manifest-path apps/desktop/src-tauri/Cargo.toml -- --check
• cargo test --manifest-path apps/desktop/src-tauri/Cargo.toml --all-targets
• cargo clippy --manifest-path apps/desktop/src-tauri/Cargo.toml --all-targets -- -D warnings
• npm run desktop:check
• npm run desktop:build
• python -m unittest discover -s sidecars/mitmproxy/tests -v
• python sidecars/mitmproxy/package_sidecar.py
• python sidecars/mitmproxy/verify_sidecar_bundle.py sidecars/mitmproxy/dist