Settings modal

Workspace preferences, anonymization defaults, signing identity, and dictionary.

Changes are persisted to local storage and re-applied at next launch.

• General — UI scale and workspace preferences.
• Viewport — rendering and display defaults.
• Anonymization & Export — the default de-identification profile and export behaviour.
• Advanced & Memory — memory ceiling and image cache size.
• Signing identity — the key used for integrity manifests; see Signing key.
• Standard docs — which DICOM dictionary backs every tag description; see Standard docs.