Write a SpacetimeDB backend module in Rust that defines a table of user profiles and a per-user view that returns only the calling user's profile.

TABLES
- profile
  - Struct: Profile
  - public table
  - Fields:
    - id: u64 (primary key, auto_inc)
    - identity: Identity (unique)
    - name: String
    - bio: String

VIEWS
- my_profile
  - per-user view (uses ViewContext, not AnonymousViewContext)
  - public
  - Returns: Option<Profile> (the single profile row matching ctx.sender(), or None)
  - Logic: look up the profile by the identity column matching ctx.sender()
