feat(capture): persist response outcomes

[kev1n77]

Summary

• extend CaptureEnvelope with sanitized response and upstream-failure outcomes, including completeness and text/SSE bodies
• migrate SQLCipher storage to schema v2 and expose status, duration, Raw, and Timeline data through the desktop API
• buffer out-of-order outcomes in Tauri and cover success, HTTP errors, failures, cancellation, SSE, migration, and credential canaries

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
• 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