[US-010] Create store profile (name, logo, bio, category)

[leimo2011]

Epic: EP-02 — Store Onboarding & Link Management \nPriority: Must Have (M) \nStory Points: 5 \nSprint: Sprint 1\n\n### User Story\nAs a store admin, I want to create my store profile (name, logo, bio, category) so users can find me.\n\n### Acceptance Criteria\n- [ ] Store admin can enter store name, upload logo, write bio\n- [ ] Store name must be unique (slug generated automatically)\n- [ ] Logo upload to S3/R2; preview shown before save\n- [ ] Store status starts as PENDING until super admin approves (or auto-active for MVP)\n- [ ] GET /api/stores/{slug}/ returns store public profile\n\n### Technical Notes\n- POST /api/stores/ — create store\n- PATCH /api/stores/{id}/ — update store\n- Image upload: multipart form / presigned S3 URL