feat(031): Maintenance Banner for Dashboards — full spec→plan→tasks package

Spec: 5 user stories (P1-P3), 17 FRs, 7 SCs, 12 edge cases, RBAC matrix
Plan: 7 research decisions, 15 semantic contracts (C1-C4)
Data: 4 SQLAlchemy models (Banner entity enforces one-chart-per-dashboard)
UX: async-only API, banner template with optional variables, admin settings UI
Tasks: 64 tasks across 8 phases, 12 reused frontend components
Workflow: component reuse scan mandated in speckit.plan/tasks + semantics-svelte
Constitution: filled with 7 architecture principles from ADRs

.opencode/command/speckit.tasks.md

@@ -117,6 +117,18 @@ Examples:
 
 If no safe executable task wording exists because the accepted path is still unclear, stop and emit `[NEED_CONTEXT: target]`.
 
+### Component Reuse Mandate
+
+Every frontend task MUST reference existing components from the design system before creating new ones. The component inventory from `contracts/modules.md` (populated during `/speckit.plan`) drives task generation:
+
+| Reuse Level | Task Wording Rule |
+|-------------|-------------------|
+| **Existing component** (e.g. `<Button>`) | Task says: "...using `<Button>` from `$lib/ui/Button.svelte` (existing)" |
+| **Existing pattern** (e.g. badge, skeleton) | Task says: "...inline Tailwind: `rounded-full px-2.5 py-0.5 text-xs font-medium bg-{color}-100` (matches DashboardHub badge convention)" |
+| **New component required** | Task says: "Implement new `ComponentName.svelte`" — only when inventory confirms no reusable asset |
+
+**Before writing any frontend task, verify:** does an existing component or page already do this? If `contracts/modules.md` maps a `@RELATION DEPENDS_ON -> [ExistingComponent]`, the task MUST use it. Never schedule "build a custom dropdown" when `<Select>` exists; never schedule "create a toast system" when `addToast()` is wired.
+
 ### Test Tasks
 
 Tests are optional only when the feature truly has no new verification surface. Test tasks are usually expected for: