Wire remaining Design tab pickers: data module shape, per-corner finder shape, logo knockout shape

`QrGenerator.razor`'s Design tab currently only exposes color pickers (foreground/background/marker) and a logo file upload. The original Phase 6 plan called for also wiring up:

- A picker for data module shape (including new polygon shapes once implemented).
- Per-corner finder marker shape pickers (not just color).
- A logo knockout shape picker.

**Scope:**
- Depends on the data-module shapes, finder-marker shapes, and logo knockout issues being implemented first (or can be scaffolded against the existing 3-shape `ModuleShape` enum and extended incrementally).
- Add corresponding UI controls (e.g. Telerik dropdowns) bound to new/existing `FritzQrCode` parameters.

Start with QrGenerator.razor to see how the Design tab's existing color pickers and logo upload are bound, then read FritzQrCode's available parameters and the prerequisite shape issues. Done means the tab has controls for data module shape, each corner's finder marker shape, and logo knockout shape, bound to the corresponding FritzQrCode parameters.

Written by the indexing model from the issue text.