Planning Implementation

Assumptions: Write plans implementation assuming the engineer has zero context. Document everything: files to touch, code to write, tests to run.

Bite-Sized Task Granularity: Each step is one atomic action:

1. "Write the failing test"
2. "Run it to make sure it fails"
3. "Implement the minimal code"
4. "Run the tests and make sure they pass"
5. "Commit"

Plan File Location: docs/plans/YYYY-MM-DD-<feature-name>.md

Plan Header Template:

# [Feature Name] Implementation Plan
**Goal:** [One sentence describing what this builds]
**Architecture:** [2-3 sentences about approach]
**Tech Stack:** [Key technologies/libraries]

Task Structure Template:

### Task N: [Component Name] (e.g., Backend Handler / Frontend Component)
**Files:**
- Create: `backend/internal/handlers/v1/new_handler.go`
- Modify: `frontend/app/(customer)/profile/page.tsx`

**Step 1: Write the failing test / Define Interface**
Define the DTO or Service interface first.

**Step 2: Implement Logic / UI**
Follow the established patterns (Clean Architecture for Backend, shadcn/ui for Frontend).

**Step 3: Verification**
Run: `go test ./...` or `npm run dev` and manual check.

**Principals**:
- Exact file paths always.
- Complete code in plan.
- Exact commands with expected output.
- DRY, YAGNI, TDD.