docs(04): create phase plan

Phase 04: Tags & Organization
- 3 plan(s) in 2 wave(s)
- Wave 1: 04-01 (tags schema), 04-02 (pin/due date) - parallel
- Wave 2: 04-03 (tag UI) - depends on 04-01
- Ready for execution

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.planning/ROADMAP.md

@@ -88,12 +88,12 @@ Plans:
   5. User can pin/favorite an entry for quick access
   6. User can set a due date on a task
   7. Pinned entries appear in a dedicated section at top of list
-**Plans**: TBD
+**Plans**: 3 plans
 
 Plans:
-- [ ] 04-01: TBD
-- [ ] 04-02: TBD
-- [ ] 04-03: TBD
+- [ ] 04-01-PLAN.md — Tags schema with case-insensitive index and tagRepository
+- [ ] 04-02-PLAN.md — Pin/favorite and due date UI (uses existing schema columns)
+- [ ] 04-03-PLAN.md — Tag input component with Svelecte autocomplete
 
 ### Phase 5: Search
 **Goal**: Users can find entries through search and filtering