docs(legibility): add 18 per-domain README.md files (DOC-6)

Backend (9): document, person, tag, user, geschichte, notification,
ocr, audit, dashboard.
Frontend (8): document, person, tag, user, geschichte, notification,
ocr, shared.
OCR service (1): ocr-service/README.md.

Each README covers: what the domain owns, explicit non-ownership,
public surface (verified by grep against the codebase), internal
layout, and cross-domain dependencies.

Closes #400
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/user/README.md

@@ -0,0 +1,28 @@
+# user (frontend)
+
+UI for account management: profile editing, password change, and permission group management in the admin panel.
+
+## What this domain owns
+
+Components: `UserProfileSection.svelte`, `UserPasswordSection.svelte`, `UserGroupsSection.svelte`.
+
+## What this domain does NOT own
+
+- `Person` records — historical family members are entirely separate from login accounts. A user editing their profile is an `AppUser`; the historical persons in documents are `Person` entities. They are never linked.
+- User list or admin creation UI — those live in the `/admin` route, which assembles views from multiple domains.
+
+## Key components
+
+| Component                    | Used in                     | Notes                                |
+| ---------------------------- | --------------------------- | ------------------------------------ |
+| `UserProfileSection.svelte`  | `/settings` or profile page | Display name, email editing          |
+| `UserPasswordSection.svelte` | `/settings`                 | Password change form                 |
+| `UserGroupsSection.svelte`   | `/admin`                    | Per-user permission group assignment |
+
+## Cross-domain imports
+
+- `shared/primitives/` — generic UI primitives only
+
+## Backend counterpart
+
+`backend/src/main/java/org/raddatz/familienarchiv/user/README.md`