docs(03-02): complete delete confirmation and empty states plan

- Create 03-02-SUMMARY.md documenting EmptyState component and delete confirmation dialog
- Update STATE.md with progress (88%), decisions, and session info
- Update ROADMAP.md with Phase 3 plan progress (3/4 summaries)

.planning/STATE.md

@@ -3,8 +3,8 @@ gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
 status: planning
-stopped_at: Completed 03-00-PLAN.md
-last_updated: "2026-03-11T21:33:29.235Z"
+stopped_at: Completed 03-02-PLAN.md
+last_updated: "2026-03-11T21:33:38.813Z"
 last_activity: 2026-03-11 — Roadmap created from requirements and research
 progress:
   total_phases: 4
@@ -81,6 +81,9 @@ Recent decisions affecting current work:
 - [Phase 03-interaction-quality-and-completeness]: Budget Edit spinner deferred — no BudgetEdit form component exists in codebase yet
 - [Phase 03-interaction-quality-and-completeness]: Mock useBudgets hook in DashboardPage tests to control loading state directly
 - [Phase 03-interaction-quality-and-completeness]: BillsTracker renders a full Card component — tests render it standalone, not inside a <tr>
+- [Phase 03-interaction-quality-and-completeness]: EmptyState is a shared component with all content as props — icon, heading, subtext, and optional CTA
+- [Phase 03-interaction-quality-and-completeness]: Delete dialog does not auto-close on error — user must read ON DELETE RESTRICT message before dismissing
+- [Phase 03-interaction-quality-and-completeness]: CategoriesPage loading state initialized true, set false in finally block to prevent empty-state flash
 
 ### Pending Todos
 
@@ -93,6 +96,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-03-11T21:33:17.674Z
-Stopped at: Completed 03-00-PLAN.md
+Last session: 2026-03-11T21:33:38.811Z
+Stopped at: Completed 03-02-PLAN.md
 Resume file: None