feat: compare limit 9, format-aware import placeholder, help links

- Raise compare limit from 8 to 9 (server + client, toast on overflow)
- Make import textarea placeholder match selected format (CSV/JSON/YAML/auto)
- Add GuideHelp links to admin create/edit user dialogs and tool import dialog

docs/releases/v0.9.2/handbook/bewerten.en.md

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+
+# Rating
+
+On the detail page of a tool you can share your experience. Click on
+**Submit a rating** (requires an account).
+
+## Form fields
+
+| Field | Required | Notes |
+| --- | --- | --- |
+| **Usefulness** | Yes | 1–5 stars |
+| **Usability** | Yes | 1–5 stars |
+| **Comment** | No | Free text |
+| **Name** | No | Defaults to "Anonymous" |
+
+Next to the fields, the **? icon** links directly to the associated field
+description in the [data model reference](/docs/reference/schemas/ratinginput).
+
+## What happens after submitting?
+
+- Your rating is saved immediately and appears in the **rating list** of the
+  detail page.
+- The **averages** (usefulness, usability, combined) and the **score
+  distribution** are updated.
+- The **statistics** in the [Analytics](/docs/handbook/analytics) section are
+  recalculated.
+
+## Statistic sections on the detail page
+
+- **Rating overview:** usefulness & usability as an average with progress
+  bars.
+- **Score distribution:** number of ratings per star (1★–5★).
+- **History:** line chart of combined/individual values over time
+  (only visible once there are several ratings).
+
+## API
+
+- [`POST /tools/{id}/ratings`](/docs/reference/endpoints/ratings#createRating) — Submit a rating
+- [`GET /tools/{id}/ratings`](/docs/reference/endpoints/ratings#listToolRatings) — Ratings of a tool