feat: add dashboards — tables, CRUD API, widget data endpoint

- New dashboards table (name, description, layout, is_default)
- New dashboard_widgets table (view_id, title, widget_type, position, config)
- GET/POST/PATCH/DELETE /dashboards
- GET/POST/PATCH/DELETE /dashboards/:id/widgets
- GET /dashboards/:id/widgets/:id/data — runs saved view filters,
  returns pre-aggregated data for count/ticket_list/status_chart/grouped_counts
- is_default uniqueness enforced on PATCH

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

drizzle/migrations/0004_sturdy_natasha_romanoff.sql

@@ -0,0 +1,22 @@
+CREATE TABLE "dashboard_widgets" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"dashboard_id" uuid NOT NULL,
+	"view_id" uuid NOT NULL,
+	"title" text NOT NULL,
+	"widget_type" text NOT NULL,
+	"position" jsonb DEFAULT '{"x":0,"y":0,"w":4,"h":2}',
+	"config" jsonb DEFAULT '{}',
+	"created_at" timestamp with time zone DEFAULT now()
+);
+--> statement-breakpoint
+CREATE TABLE "dashboards" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"name" text NOT NULL,
+	"description" text,
+	"layout" jsonb DEFAULT '[]',
+	"is_default" boolean DEFAULT false,
+	"created_at" timestamp with time zone DEFAULT now()
+);
+--> statement-breakpoint
+ALTER TABLE "dashboard_widgets" ADD CONSTRAINT "dashboard_widgets_dashboard_id_dashboards_id_fk" FOREIGN KEY ("dashboard_id") REFERENCES "public"."dashboards"("id") ON DELETE cascade ON UPDATE no action;--> statement-breakpoint
+ALTER TABLE "dashboard_widgets" ADD CONSTRAINT "dashboard_widgets_view_id_views_id_fk" FOREIGN KEY ("view_id") REFERENCES "public"."views"("id") ON DELETE cascade ON UPDATE no action;