feat(backend): add instance path and token generation utilities

Author: Lasim

services/backend/drizzle/migrations/0026_happy_carnage.sql

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+ALTER TABLE "mcpServerInstances" ADD COLUMN "instance_path" text;--> statement-breakpoint
+ALTER TABLE "mcpServerInstances" ADD COLUMN "instance_token" text;--> statement-breakpoint
+CREATE UNIQUE INDEX "mcp_instances_instance_path_idx" ON "mcpServerInstances" USING btree ("instance_path");