[Feature] Add granular "Deny Original Download" permission for local instance users in Shared Albums

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes The feature Is your feature request related to a problem? Please describe. Currently, when sharing an album with an existing local Immich account, the lowest assignable permission tier is Viewer (read-only). This role implicitly allows the user to download original, high-resolution source files. Describe the solution you'd like I propose introducing a new checkbox or permission tier for local user sharing: "Deny Original Download" (similar to the toggle currently available for Public Share Links). • How it should work: When enabled for a specific local user or group on a shared album, the native Immich mobile app and web UI should hide the "Download" button. The server should only serve compressed/downscaled web-optimized previews (.webp / JPEGs) to their client timeline and interface, blocking direct API pipeline acce…