Let resolve_product run fully for POST, just skip redirects

Instead of skipping resolve_product entirely for POST (leaving
g.item_data unset and breaking templates), run the full resolution
but suppress canonical-slug redirects. This sets g.item_data for
the context processor so d.slug and other template vars work.

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

bp/product/routes.py

@@ -48,9 +48,7 @@ def register():
         if raw_slug is None:
             return
 
-        # POST endpoints (cart, like) only need the slug — skip redirects
-        if req.method == "POST":
-            return
+        is_post = req.method == "POST"
 
         # 1. If slug is INT → load product by ID
         if raw_slug.isdigit():
@@ -69,18 +67,22 @@ def register():
                 g.item_data = {"d": d, "slug": product["slug"], "liked": False}
                 return
 
-            # Not deleted → redirect to canonical slug
+            # Not deleted → redirect to canonical slug (GET only)
+            if not is_post:
                 canon = canonical_html_slug(product["slug"])
                 return redirect(
                     host_url(url_for("market.browse.product.product_detail", slug=canon))
                 )
 
+            g.item_data = {"d": product, "slug": product["slug"], "liked": False}
+            return
+
         # 2. Normal slug-based behaviour
         if is_product_blocked(raw_slug):
             abort(404)
 
         canon = canonical_html_slug(raw_slug)
-        if canon != raw_slug:
+        if canon != raw_slug and not is_post:
             return redirect(
                 host_url(url_for("market.browse.product.product_detail", slug=canon))
             )
@@ -91,7 +93,7 @@ def register():
         )
         if not d:
             abort(404)
-        g.item_data = {"d": d, "slug": canon, "liked": d["is_liked"]}
+        g.item_data = {"d": d, "slug": canon, "liked": d.get("is_liked", False)}
 
     @bp.context_processor
     def context():
@@ -265,7 +267,6 @@ def register():
 
             return await render_template(
                 "_types/product/_added.html",
-                d={"slug": slug},
                 cart=g.cart,
                 item=ci,
                 total=total,