Migrate remaining Component() callers to Element; delete the shim

The legacy back-compat ``Component(tag_name=...)`` function (a thin
string-returning wrapper over ``Element``) was the last piece of the
pre-node-tree API. Migrate its ~18 call sites across the views to the node
builders and remove it:

- stats_content.py: the table helpers now use the whitelisted ``Td`` / ``Th``
  / ``Tr`` builders and ``Element`` for table/tbody/thead/h1; helper return
  types are ``Node``.
- auth.py / statuschange.py / game.py / purchase.py: the hand-built
  ``<form>`` / ``<button>`` / ``<h1>`` / ``<h2>`` / ``<table>`` markup now uses
  ``Element("tag", ...)``.
- core.py: drop the ``Component()`` function and its back-compat note;
  ``common/components/__init__`` no longer exports it.
- Tests that exercised the shim now target ``Element`` directly
  (test_components cache/escaping/edge-case classes; test_node_tree drops the
  legacy-parity and legacy-bridge cases, which ``Element`` coverage subsumes).
- CLAUDE.md: drop the "legacy Component retained for back-compat" notes.

Full suite green (443; one obsolete legacy-bridge test removed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

games/views/purchase.py

@@ -19,14 +19,15 @@ from common.components import (
     AddForm,
     Button,
     ButtonGroup,
-    Component,
     CsrfInput,
     Div,
+    Element,
     GameLink,
     Icon,
     LinkedPurchase,
     Modal,
     ModuleScript,
+    Node,
     PriceConverted,
     PurchasePrice,
     TableRow,
@@ -301,9 +302,9 @@ def drop_purchase(request: HttpRequest, purchase_id: int) -> HttpResponse:
     return redirect("games:list_purchases")
 
 
-def _refund_confirmation_modal(purchase_id: int, request: HttpRequest) -> SafeText:
-    form = Component(
-        tag_name="form",
+def _refund_confirmation_modal(purchase_id: int, request: HttpRequest) -> Node:
+    form = Element(
+        "form",
         attributes=[
             ("hx-post", reverse("games:refund_purchase", args=[purchase_id])),
             ("hx-target", f"#purchase-row-{purchase_id}"),
@@ -339,8 +340,8 @@ def _refund_confirmation_modal(purchase_id: int, request: HttpRequest) -> SafeTe
     return Modal(
         "refund-confirmation-modal",
         children=[
-            Component(
-                tag_name="h1",
+            Element(
+                "h1",
                 attributes=[
                     (
                         "class",