Move low-stock warning from image badge to a text hint, add it to the cart

The image-overlaid pill made the low-stock message read as clutter on
product photos and had no equivalent in the cart at all. It's now a text
line next to the price (ProductGrid/ProductSpotlight/RelatedProducts/
Pricing) and under the product name in cart line items (variant-specific,
not "any variant low"). The line's height is always reserved, not
conditionally rendered, so cards in the same row stay equal-height
regardless of low-stock state — the exact regression an earlier text-based
version of this hint caused before it was replaced by the image badge.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -393,24 +393,29 @@ own distinct badge, the two never combine), and at/below the product's own
 `lowStockThreshold`. Neither raw `stock` nor `lowStockThreshold` is
 exposed in the public `Product` type, only this derived boolean — the
 public API has no reason to leak exact counts. Shown as a "Nur noch wenige
-verfügbar" pill (a new `--color-warning` token in `globals.css`, distinct
-from the brand-colored discount badge so the two never read as the same
-thing) — the same image-overlaid top-left pill Ausverkauft/discount
-already use (`position: absolute`, outside layout flow) on
-`ProductGrid.tsx`/`ProductSpotlight.tsx`/`RelatedProducts.tsx`/todo-cards'
-`Pricing.tsx`, plus a `"(nur noch wenige)"` variant-select suffix in
-`AddToCartButton`/`AddToCartInlineButton`. Stacks with the discount badge
-in a `flex flex-col` column rather than being replaced by it — a
-discounted product that's also low on stock (both are independent
-booleans, not mutually exclusive states) needs to show both, discovered
-live when `todo-karten` had exactly that combination and the low-stock
-pill silently never rendered under the old either/or ternary. Only
-"Ausverkauft" still wins outright, since it replaces both. Deliberately
-**not** a separate
-text line under the add-to-cart button (an earlier version did this) —
-that made the button block's own height vary card-to-card in every grid
-rendering it, breaking equal-height card alignment; the badge doesn't
-participate in layout flow at all, so it can't cause that.
+verfügbar" **text line** (`text-warning`, the same `--color-warning` token
+in `globals.css`, distinct from the brand-colored discount badge) next to
+the price on `ProductGrid.tsx`/`ProductSpotlight.tsx`/
+`RelatedProducts.tsx`/todo-cards' `Pricing.tsx` and — variant-specific, not
+"any variant low" — under the product name in `CartContent.tsx`'s own
+cart line items, plus the existing `"(nur noch wenige)"` variant-select
+suffix in `AddToCartButton`/`AddToCartInlineButton`. The image-overlaid
+top-left pill (`position: absolute`, outside layout flow) now shows only
+Ausverkauft/discount — low-stock moved off the image into text on request,
+since a shopper scanning product photos for "-20%" style badges reads a
+long low-stock sentence pinned to the image as clutter, and a customer
+already in the cart with that product had no low-stock signal there at
+all before this. The earlier version of this text line (removed once,
+see git history) broke equal-height card alignment in `ProductGrid.tsx`/
+`RelatedProducts.tsx` by only rendering when `lowStock` was true, so
+cards with/without the line ended up different heights; this version
+always renders the line's slot (`min-h-[1.05rem]`, empty when not
+low-stock) so every card in a row reserves the same space regardless of
+state — `ProductGrid.tsx` additionally still has its `flex-1` spacer
+pinning the add-to-cart button to the same Y as before, so the reserved
+height is belt-and-suspenders there, but load-bearing in
+`RelatedProducts.tsx`, which has no such spacer. Only "Ausverkauft" still
+wins outright over the discount pill, since it replaces it.
 
 **Pricing**: `app/lib/cartTotals.ts`'s `effectivePrice(entry, product)` —
 a selected variant's `priceOverride` wins over the base `product.price`