[Nostr] Rebuild permissions table for strict per-profile isolation

[shadowbipnode]

Rebuild nostr_permissions to remove the legacy UNIQUE(origin, action) constraint and enforce UNIQUE(profile_id, origin, action).

Current state:

• profile_id column exists
• application helpers query by active profile_id
• unique index on (profile_id, origin, action) exists
• legacy UNIQUE(origin, action) still exists from the original table schema

Goal:

• safely migrate existing permissions into a new table
• preserve existing permission rows
• remove legacy global uniqueness constraint
• enforce strict per-profile NIP-07 permission isolation

This should be done carefully because it touches security-sensitive NIP-07 permission persistence.