feat: remove ProjectMember, add expose RBAC role, attach/detach-server commands

- Remove ProjectMember model entirely (RBAC manages project access)
- Add 'expose' RBAC role for /mcp-config endpoint access (edit implies expose)
- Rename CLI flags: --llm-provider → --proxy-mode-llm-provider, --llm-model → --proxy-mode-llm-model
- Add attach-server / detach-server CLI commands (mcpctl --project NAME attach-server SERVER)
- Add POST/DELETE /api/v1/projects/:id/servers endpoints for server attach/detach
- Remove members from backup/restore, apply, get, describe
- Prisma migration to drop ProjectMember table

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/db/prisma/migrations/20260223120000_remove_project_members/migration.sql

@@ -0,0 +1,8 @@
+-- DropForeignKey
+ALTER TABLE "ProjectMember" DROP CONSTRAINT IF EXISTS "ProjectMember_projectId_fkey";
+
+-- DropForeignKey
+ALTER TABLE "ProjectMember" DROP CONSTRAINT IF EXISTS "ProjectMember_userId_fkey";
+
+-- DropTable
+DROP TABLE IF EXISTS "ProjectMember";