reflex-site-shared: add canonical override + Streamlit migration footer link

- create_meta_tags grows an optional `canonical` kwarg so any consumer
  (blog post, lander) can declare a different canonical URL than the
  page's own. Default behavior is unchanged when the kwarg is omitted.
- Footer Migration column gets a "From Streamlit" entry pointing at
  /migration/streamlit/, ordered first to surface the most specific
  target.

Pairs with:
- reflex-dev/marketing PR adding the /migration/streamlit lander.
- reflex-dev/blog PR refreshing /blog/reflex-streamlit with a frontmatter
  canonical override that consumes the new kwarg.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 2 people

packages/reflex-site-shared/src/reflex_site_shared/meta/meta.py

@@ -126,7 +126,11 @@ def to_cdn_image_url(image: str | None) -> str:
 
 
 def create_meta_tags(
-    title: str, description: str, image: str | None, url: str | None = None
+    title: str,
+    description: str,
+    image: str | None,
+    url: str | None = None,
+    canonical: str | None = None,
 ) -> list[dict[str, str] | rx.Component]:
     """Create meta tags for a page.
 
@@ -135,6 +139,10 @@ def create_meta_tags(
         description: The page description.
         image: The image path for social media previews (None to omit).
         url: The page URL (optional, defaults to REFLEX_DOMAIN_URL).
+        canonical: Override for the canonical link. Use when one page should
+            consolidate SEO signals to a different URL (for example, a blog
+            post that canonicalizes to a dedicated comparison lander). Leave
+            None to canonicalize to ``url``.
 
     Returns:
         A list of meta tag dictionaries.
@@ -149,7 +157,7 @@ def create_meta_tags(
             image=image_url,
             url=page_url,
         ),
-        rx.el.link(rel="canonical", href=page_url),
+        rx.el.link(rel="canonical", href=canonical or page_url),
     ]
 
 

packages/reflex-site-shared/src/reflex_site_shared/views/footer.py

@@ -295,6 +295,7 @@ def footer_index(class_name: str = "", grid_class_name: str = "") -> rx.Componen
                         footer_link_flex(
                             "Migration",
                             [
+                                footer_link("From Streamlit", "/migration/streamlit/"),
                                 footer_link("From No-Code", "/migration/no-code/"),
                                 footer_link("From Low-Code", "/migration/low-code/"),
                                 footer_link(