docs(ui): Add UI layout refactor plan and OpenSpec changes

- Update decision-log with UI layout decisions (Feb 18, 2026)
- Update architecture with frontend layout patterns
- Update config.yaml with TDD, documentation, UI standards rules
- Create p00-api-documentation change (Scribe annotations)
- Create p01-ui-foundation change (types, stores, Lucide)
- Create p02-app-layout change (AppLayout, Sidebar, TopBar)
- Create p03-dashboard-enhancement change (PageHeader, StatCard)
- Create p04-content-patterns change (DataTable, FilterBar)
- Create p05-page-migrations change (page migrations)
- Fix E2E auth tests (11/11 passing)
- Add JWT expiry validation to dashboard guard

openspec/changes/p04-content-patterns/proposal.md

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+# Proposal: Content Patterns
+
+## Overview
+Create reusable content components for data-dense views: DataTable, FilterBar, EmptyState, and LoadingState.
+
+## Goals
+- Create DataTable component wrapping TanStack Table with DaisyUI styling
+- Create FilterBar component for reusable filter patterns
+- Create EmptyState component for no-data placeholders
+- Create LoadingState component with skeleton patterns
+
+## Non-Goals
+- Page implementations (done in p05)
+- Specific business logic
+
+## Priority
+**MEDIUM** - Reusable patterns for pages
+
+## Scope
+
+### DataTable Component
+- Wraps @tanstack/svelte-table
+- DaisyUI table styling
+- Sorting support
+- Pagination support
+- Row selection (optional)
+- Loading state
+- Empty state integration
+
+### FilterBar Component
+- Search input
+- Filter dropdowns
+- Date range picker integration
+- Clear filters button
+- Slot for custom filters
+
+### EmptyState Component
+- Icon display
+- Title and description
+- Optional action button
+- Consistent styling
+
+### LoadingState Component
+- Skeleton patterns for different content types
+- Table skeleton
+- Card skeleton
+- Text skeleton
+
+## Success Criteria
+- [ ] DataTable created with TanStack integration
+- [ ] FilterBar created with search and dropdowns
+- [ ] EmptyState created with icon and action
+- [ ] LoadingState created with skeletons
+- [ ] All tests pass
+
+## Estimated Effort
+3-4 hours
+
+## Dependencies
+- p02-app-layout
+- p03-dashboard-enhancement (can start in parallel)
+
+## Blocks
+- p05-page-migrations