feat(dashboard): dashboard_layout table + repo

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

lib/db/migrations/012_dashboard_layout.sql

@@ -0,0 +1,10 @@
+-- 012_dashboard_layout.sql
+-- Single global, owner-scoped dashboard layout. One logical row keyed by a
+-- stable owner key (v2 is single-owner; 'owner' is the only key for now).
+CREATE TABLE dashboard_layout (
+  owner_key   text PRIMARY KEY DEFAULT 'owner',
+  card_order  jsonb NOT NULL DEFAULT '[]'::jsonb,   -- ["clock","weather",...]
+  hidden      jsonb NOT NULL DEFAULT '[]'::jsonb,   -- ["speedtest"]
+  sizes       jsonb NOT NULL DEFAULT '{}'::jsonb,   -- {"weather":"s"}
+  updated_at  timestamptz NOT NULL DEFAULT now()
+);