feat(web): restore payload CMS (cuidecar pattern + importMap)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/db/migrations/0011_add-streams.sql

@@ -0,0 +1,10 @@
+CREATE TABLE "mesh"."stream" (
+	"id" text PRIMARY KEY NOT NULL,
+	"mesh_id" text NOT NULL,
+	"name" text NOT NULL,
+	"created_by_name" text,
+	"created_at" timestamp DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+ALTER TABLE "mesh"."stream" ADD CONSTRAINT "stream_mesh_id_mesh_id_fk" FOREIGN KEY ("mesh_id") REFERENCES "mesh"."mesh"("id") ON DELETE cascade ON UPDATE cascade;--> statement-breakpoint
+CREATE UNIQUE INDEX "stream_mesh_name_idx" ON "mesh"."stream" USING btree ("mesh_id","name");