docs(38): create phase plans for admin tag management

Two plans across 2 waves: backend (schema + service + routes + tests)
then frontend (hooks + tree list page + edit page + sidebar activation).

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

.planning/ROADMAP.md

@@ -96,7 +96,7 @@
 
 </details>
 
-### 🚧 v2.4 Admin Foundation (In Progress)
+### v2.4 Admin Foundation (In Progress)
 
 - [x] **Phase 35: Bug Fixes** — Clear the v2.3 backlog: wrong modal, missing images, slow loading, auth redirect, cursor pointer (completed 2026-04-19)
 - [x] **Phase 36: Admin Role & Panel Foundation** — isAdmin flag, server mechanism to grant admin, gated /admin route with placeholder UI (completed 2026-04-19)
@@ -276,7 +276,11 @@ Plans:
   4. Admin can assign a parent to any tag, making it a child in the hierarchy (e.g. "down" under "insulation")
   5. Admin can remove a parent assignment from a tag, making it a top-level tag again
   6. Admin can delete a tag; if items currently use that tag, a warning is shown before the deletion is confirmed
-**Plans**: TBD
+**Plans**: 2 plans
+
+Plans:
+- [ ] 38-01-PLAN.md — Schema migration (parentId), service layer (CRUD + cycle detection), API routes, tests
+- [ ] 38-02-PLAN.md — Client hooks, tag list page (tree view + quick-add + search), edit page (rename/reparent/delete), sidebar activation
 
 **UI hint**: yes
 
@@ -321,7 +325,7 @@ Plans:
 | 35. Bug Fixes | v2.4 | 3/3 | Complete   | 2026-04-19 |
 | 36. Admin Role & Panel Foundation | v2.4 | 2/2 | Complete   | 2026-04-19 |
 | 37. Admin — Global Item Management | v2.4 | 0/TBD | Not started | - |
-| 38. Admin — Tag Management | v2.4 | 0/TBD | Not started | - |
+| 38. Admin — Tag Management | v2.4 | 0/2 | Not started | - |
 
 ## Backlog