Replace JSON sx-headers with SX dict expressions, fix blog like component

sx-headers attributes now use native SX dict format {:key val} instead of
JSON strings. Eliminates manual JSON string construction in both .sx files
and Python callers.

- sx.js: parse sx-headers/sx-vals as SX dict ({: prefix) with JSON fallback,
  add _serializeDict for dict→attribute serialization, fix verbInfo scope in
  _doFetch error handler
- html.py: serialize dict attribute values via SX serialize() not str()
- All .sx files: {:X-CSRFToken csrf} replaces (str "{\"X-CSRFToken\": ...}")
- All Python callers: {"X-CSRFToken": csrf} dict replaces f-string JSON
- Blog like: extract ~blog-like-toggle, fix POST returning wrong component,
  fix emoji escapes in .sx (parser has no \U support), fix card :hx-headers
  keyword mismatch, wrap sx_content in SxExpr for evaluation

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

events/sxc/pages/entries.py

@@ -552,7 +552,7 @@ def render_entry_posts_panel(entry_posts, entry, calendar, day, month, year) ->
             items += sx_call("events-entry-post-item",
                             img=img_html, title=ep_title,
                             del_url=del_url, entry_id=eid_s,
-                            csrf_hdr=f'{{"X-CSRFToken": "{csrf}"}}')
+                            csrf_hdr={"X-CSRFToken": csrf})
         posts_html = sx_call("events-entry-posts-list", items=SxExpr(items))
     else:
         posts_html = sx_call("events-entry-posts-none")