Scoping connectors per tenant

Not every tenant should see or use every integration. Key points:

• Connectors carry a scope. Platform-internal connectors (billing, the model provider, the secrets backend) stay out of the tenant marketplace.
• Scope what each tenant can use so a tenant's marketplace shows the tools that belong to it, not the whole catalog.
• Consolidate per-tool: one tool that has several capability connectors should read as one entry, so a tenant picks "the GitLab integration", not three near-duplicate rows.