Convert social and federation profile from Jinja to SX rendering

Add primitives (replace, strip-tags, slice, csrf-token), convert all
social blueprint routes and federation profile to SX content builders,
delete 12 unused Jinja templates and social_lite layout.

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

shared/sx/primitives.py

@@ -257,6 +257,24 @@ def prim_split(s: str, sep: str = " ") -> list[str]:
 def prim_join(sep: str, coll: list) -> str:
     return sep.join(str(x) for x in coll)
 
+@register_primitive("replace")
+def prim_replace(s: str, old: str, new: str) -> str:
+    return s.replace(old, new)
+
+@register_primitive("strip-tags")
+def prim_strip_tags(s: str) -> str:
+    """Strip HTML tags from a string."""
+    import re
+    return re.sub(r"<[^>]+>", "", s)
+
+@register_primitive("slice")
+def prim_slice(coll: Any, start: int, end: Any = None) -> Any:
+    """Slice a string or list: (slice coll start end?)."""
+    start = int(start)
+    if end is None or end is NIL:
+        return coll[start:]
+    return coll[start:int(end)]
+
 @register_primitive("starts-with?")
 def prim_starts_with(s, prefix: str) -> bool:
     if not isinstance(s, str):