docs(legibility): migrate CLAUDE.md rules into human docs — DOC-7

Processes all 7 CLAUDE.md files according to the 3-bucket classification.
Migration targets (CONTRIBUTING.md, docs/ARCHITECTURE.md, docs/DEPLOYMENT.md,
domain READMEs) are introduced by DOC-2/4/5/6 — this PR must merge last.

### scripts/CLAUDE.md → scripts/README.md
New `scripts/README.md` with full script documentation (preserving the
⚠️ destructive-operation warning on reset-db.sh). `scripts/CLAUDE.md`
reduced to a pointer + "document new scripts in README.md" reminder.

### .devcontainer/CLAUDE.md → .devcontainer/README.md
New `.devcontainer/README.md` with all configuration, usage, and limitations.
`devcontainer/CLAUDE.md` reduced to a single pointer line.

### docs/CLAUDE.md → docs/README.md
New `docs/README.md` covering the folder structure, ADR guide, infrastructure
docs, and specs folder. `docs/CLAUDE.md` reduced to pointer + ADR reminder.

### ocr-service/CLAUDE.md
Reduced to pointer to `ocr-service/README.md` (content migrated in DOC-6).
Kept LLM reminders: single-node constraint, ALLOWED_PDF_HOSTS SSRF risk.

### backend/CLAUDE.md
- Layering Rules → pointer to docs/ARCHITECTURE.md
- Error Handling → pointer to CONTRIBUTING.md + reminder
- Security/Permissions → pointer to docs/ARCHITECTURE.md + reminder
- Package Structure → tagged TODO post-REFACTOR-1
- Fixed errors.ts path to frontend/src/lib/shared/errors.ts
- Added ANNOTATE_ALL + BLOG_WRITE to permission list
- Key Entities, Entity Code Style, Services → kept (Bucket-2)

### root CLAUDE.md
- Stack, Infrastructure, Dev Container → pointers
- Layering Rules, Error Handling, Security, OpenAPI, API Client,
  Date Handling, UI Components, Frontend Error Handling → pointers + reminders
- Package Structure → tagged TODO post-REFACTOR-1
- Domain Model, Entity Code Style, Form Actions, Styling → kept (Bucket-2)

### frontend/CLAUDE.md
- API Client Pattern, Date Handling → pointers + reminders
- Key UI Components → pointer to domain READMEs
- Styling, Form Actions, How to Run, Vite Proxy, i18n → kept (Bucket-2)

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

frontend/CLAUDE.md

@@ -71,29 +71,13 @@ src/
 └── ...                  # Other SvelteKit config files
 ```
 
+For per-domain component inventories, see the domain READMEs in `src/lib/<domain>/README.md`.
+
 ## API Client Pattern
 
-All server-side API calls use the typed client from `$lib/api.server.ts`:
+→ See [CONTRIBUTING.md §Frontend API client](../CONTRIBUTING.md#frontend-api-client)
 
-```typescript
-const api = createApiClient(fetch);
-const result = await api.GET('/api/persons/{id}', { params: { path: { id } } });
-
-// Always check via response.ok, NOT result.error
-if (!result.response.ok) {
-	const code = (result.error as unknown as { code?: string })?.code;
-	throw error(result.response.status, getErrorMessage(code));
-}
-return { person: result.data! };
-```
-
-Key rules:
-
-- Use `!result.response.ok` for error checking (not `if (result.error)` — breaks when spec has no error responses defined)
-- Cast errors as `result.error as unknown as { code?: string }` to extract backend error code
-- Use `result.data!` after an ok check
-
-For multipart/form-data (file uploads), bypass the typed client and use raw `fetch`.
+**LLM reminder:** check `!result.response.ok` (not `result.error` — breaks when spec has no error responses); cast errors as `result.error as unknown as { code?: string }`; use `result.data!` after an ok check. For multipart/form-data (file uploads), bypass the typed client and use raw `fetch`.
 
 ## Form Actions Pattern
 
@@ -102,7 +86,7 @@ For multipart/form-data (file uploads), bypass the typed client and use raw `fet
 export const actions = {
 	default: async ({ request, fetch }) => {
 		const formData = await request.formData();
-		const name = formData.get('name') as string;
+		const name = formData.get('name') as string; // cast needed — FormData returns FormDataEntryValue
 		// ...
 		return fail(400, { error: 'message' }); // on error
 		throw redirect(303, '/target'); // on success
@@ -112,13 +96,9 @@ export const actions = {
 
 ## Date Handling
 
-- **Forms**: German format `dd.mm.yyyy` with auto-dot insertion via `handleDateInput()`. A hidden `<input type="hidden" name="documentDate" value={dateIso}>` sends ISO to the backend.
-- **Display**: Always use `Intl.DateTimeFormat` with `T12:00:00` suffix to prevent UTC off-by-one:
-  ```typescript
-  new Intl.DateTimeFormat('de-DE', { day: 'numeric', month: 'long', year: 'numeric' }).format(
-  	new Date(doc.documentDate + 'T12:00:00')
-  );
-  ```
+→ See [CONTRIBUTING.md §Date handling](../CONTRIBUTING.md#date-handling)
+
+**LLM reminder:** always append `T12:00:00` when constructing `new Date()` from an ISO date string — prevents UTC timezone off-by-one errors. Forms use German `dd.mm.yyyy` format via `handleDateInput()` with a hidden ISO input.
 
 ## Styling Conventions (Tailwind CSS 4)
 
@@ -146,15 +126,9 @@ Card pattern for content sections:
 
 ## Key UI Components
 
-| Component            | Location                       | Props                                   | Description                                |
-| -------------------- | ------------------------------ | --------------------------------------- | ------------------------------------------ |
-| `PersonTypeahead`    | `$lib/person/`                 | `name`, `label`, `value`, `initialName` | Single-person selector with typeahead      |
-| `PersonMultiSelect`  | `$lib/person/`                 | `selectedPersons` (bind)                | Chip-based multi-person selector           |
-| `TagInput`           | `$lib/tag/`                    | `tags` (bind), `allowCreation?`         | Tag chip input with typeahead              |
-| `PdfViewer`          | `$lib/document/`               | `url`, `annotations`                    | PDF rendering with annotation overlay      |
-| `TranscriptionBlock` | `$lib/document/transcription/` | `block`, `mode`                         | Read/edit transcription block              |
-| `DocumentTopBar`     | `$lib/document/`               | `document`                              | Responsive document metadata header        |
-| `BackButton`         | `$lib/shared/primitives/`      | —                                       | Calls `history.back()`; 44 px touch target |
+→ See per-domain READMEs: [`src/lib/person/README.md`](src/lib/person/README.md), [`src/lib/tag/README.md`](src/lib/tag/README.md), [`src/lib/document/README.md`](src/lib/document/README.md), [`src/lib/shared/README.md`](src/lib/shared/README.md)
+
+**LLM reminder:** `BackButton` is at `$lib/shared/primitives/BackButton.svelte` — use it for all back navigation; never a static `<a href>`. API client is at `$lib/shared/api.server`.
 
 ## How to Run