Replaced single `url` parameter with explicit `url_name` (URL pattern name resolved via `reverse()`) and `href` (literal path). Fixes:
- Silent fallback (typos like `"ad_puchase"` silently became broken links) → now raises `NoReverseMatch` at render time
- `type(url) is str` gate → removed (implicit dual-mode eliminated entirely)
- Callable parameter (`url: Callable`) dead code → removed
- Implicit dual-mode (`url="name"` vs `url=reverse("name")`) → `url_name` vs `href` are now mutually exclusive params
- Inconsistent type annotation mixing `Callable` with string default → cleaned up
- Added `ValueError` when both `url_name` and `href` are provided
- Updated all 10 call sites across 6 view files and internal callers (`LinkedPurchase()`, `NameWithIcon()`)
A leftover from when there was only the A component function,
this bug was not found earlier because we used
templates instead of tags most of the time.
lukas
