feat: Implement routines feature with CRUD operations and child assignment

- Add backend routines management with add, get, update, delete, and list functionalities.
- Create models for Routine, RoutineItem, RoutineSchedule, and RoutineExtension.
- Develop event types for routine confirmation and modification.
- Implement frontend components for routine assignment, confirmation dialog, and routine management views.
- Add unit tests for routine API and integration tests for routine CRUD flow.
- Create end-to-end test plan for routines feature covering parent and child interactions.

frontend/e2e/plans/routines-feature.plan.md

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+# Routines Feature E2E Plan
+
+## Application Overview
+
+The routines feature adds a new parent-defined checklist entity that sits between chores and rewards in child mode. A routine is confirmed as a whole (not per-item), then approved or rejected by the parent. Routine visibility and state are schedule-aware, include deadline extension support, and support per-child point overrides.
+
+This plan is intentionally implementation-driven so we can incrementally add tests as each phase ships.
+
+---
+
+## Coverage Areas
+
+### 1. Parent Routine Library Management
+
+File target: e2e/mode_parent/routines/routine-library.spec.ts
+
+1. Parent can create a routine with name, points, image.
+2. Parent can add multiple routine items and persist item order.
+3. Parent can edit routine metadata and item metadata.
+4. Parent can delete a routine item.
+5. Parent can delete a routine and it disappears from routine library list.
+
+### 2. Parent Child Assignment and Management
+
+File target: e2e/mode_parent/routines/routine-assignment.spec.ts
+
+1. Parent can assign routine to a child from assignable list.
+2. Parent can remove routine assignment from child.
+3. Parent can set/replace full routine assignment list for a child.
+4. Parent can set routine point override and child-facing value reflects override.
+5. Parent can set routine schedule and update it later.
+6. Parent can extend routine deadline for today.
+
+### 3. Child Routine Rendering and Navigation
+
+File target: e2e/mode_child/routines/routine-visibility.spec.ts
+
+1. Routines list renders between chores and rewards.
+2. Clicking a routine opens routine detail route (/child/:id/routine/:routineId).
+3. Detail view shows routine image, title, points, and non-interactive item list.
+4. Back navigation returns to child main view.
+
+### 4. Child Routine Confirmation Flow
+
+File target: e2e/mode_child/routines/routine-confirmation.spec.ts
+
+1. Child can mark routine Done; routine becomes pending.
+2. Child can cancel a pending routine confirmation.
+3. Child cannot submit duplicate pending confirmations.
+4. Approved-today routine shows completed state on child UI.
+5. Rejected routine returns to available state.
+
+### 5. Parent Pending Confirmation Flow
+
+File target: e2e/mode_parent/routines/routine-approval.spec.ts
+
+1. Routine confirmation appears in parent notification/pending list.
+2. Parent can approve routine; child points increase by default routine points.
+3. Parent can reject routine; child points do not change.
+4. Parent can reset approved/rejected routine to clear completion state.
+5. If routine override exists, approval uses override points instead of base points.
+
+### 6. Routine Scheduling and Deadline Behavior
+
+File target: e2e/mode_child/routines/routine-schedule.spec.ts
+
+1. Day-based schedules only show routines on scheduled days.
+2. Interval schedules show/hide routines on expected interval dates.
+3. Routine with deadline in the past displays TOO LATE and blocks Done.
+4. Extending deadline removes TOO LATE state for that day.
+5. Changing schedule resets stale pending status.
+
+### 7. Cascade and Data Integrity
+
+File target: e2e/mode_parent/routines/routine-cascade.spec.ts
+
+1. Deleting routine removes it from all assigned children.
+2. Deleting routine removes routine items.
+3. Deleting routine removes routine schedules and extensions.
+4. Deleting routine removes routine point overrides.
+5. Deleting child removes child routine schedules/extensions/overrides.
+
+### 8. SSE Reactivity
+
+File target: e2e/multi-session/routines/routine-sse.spec.ts
+
+1. Parent routine add/edit/delete updates child assignment views without refresh.
+2. Child routine pending/approved/rejected/reset updates parent notification UI without refresh.
+3. Schedule/extension changes update child routine card state without refresh.
+4. Override changes update points display without refresh.
+
+---
+
+## Test Data and Execution Notes
+
+1. Use API seeding in beforeAll and cleanup in afterAll per spec file.
+2. Use stable role/label-based locators only.
+3. Avoid /auth/login navigation in tests; rely on global storageState.
+4. For time-sensitive schedule tests, set deterministic times (or use clock controls where practical).
+
+---
+
+## Unit Test Expansion Checklist
+
+### Backend unit tests to add during implementation
+
+1. Routine CRUD API validation and ownership checks.
+2. Routine item CRUD and ordering behavior.
+3. Child routine assignment list and assignable-list filtering.
+4. Routine confirmation approve/reject/reset state transitions.
+5. Routine schedule and extension endpoints (including duplicate extension conflict).
+6. Routine deletion cascades (items/schedules/extensions/overrides/child assignments).
+
+### Frontend unit tests to add during implementation
+
+1. API helper coverage for routine endpoints.
+2. ScheduleModal entityType routing behavior for task vs routine.
+3. Child routine list sorting/filtering utility behavior.
+4. Routine detail confirmation UI state transitions.
+5. Parent pending confirmation card rendering for entity_type='routine'.