fix(backend): create instances and assign satellite for OAuth MCP server installations

The OAuth callback flow was missing instance creation and satellite
assignment that the normal installation flow (create.ts) already had.
This caused OAuth-requiring servers (Notion, Neon, Box, Linear) to have
null satellite_id and no entries in mcpServerInstances, so the satellite
never spawned processes for them.

- Add satellite_id column to oauthPendingFlows table to carry it through
  the OAuth redirect flow (authorize -> popup -> callback)
- Add satellite_id to OAuth authorize request schema and validate it
  using SatelliteValidationService with autoSelect, matching create.ts
- Set satellite_id on the installation record from the pending flow
- Create instance for installing user with status 'connecting' after
  successful OAuth token exchange
- Create instances for other team members with status
  'awaiting_user_config' so they can complete their own OAuth

Author: Lasim

services/backend/drizzle/migrations/0025_fancy_lilith.sql

@@ -0,0 +1,2 @@
+ALTER TABLE "oauthPendingFlows" ADD COLUMN "satellite_id" text;--> statement-breakpoint
+ALTER TABLE "oauthPendingFlows" ADD CONSTRAINT "oauthPendingFlows_satellite_id_satellites_id_fk" FOREIGN KEY ("satellite_id") REFERENCES "public"."satellites"("id") ON DELETE set null ON UPDATE no action;