Make component return types honest; drop str/mark_safe leftovers

Cleanup of hacky leftovers from the node-tree migration (no behaviour
change):

- Return annotations: the component builders return Node subtrees, not
  SafeText strings, but ~40 functions still declared `-> SafeText`. Correct
  them to `-> Node` across filters / search_select / date_range_picker /
  domain. The genuine string returners keep `-> SafeText`: the Alpine
  selectors (GameStatusSelector / SessionDeviceSelector, which build f-string
  markup) and the script-tag helpers (CsrfInput / ModuleScript /
  ExternalScript / StaticScript).
- layout.render_page / layout.Page / AddForm now accept `Node` in their
  `content` / `scripts` / `fields` parameters (TYPE_CHECKING import in
  layout to avoid the components import cycle), matching what views already
  pass.
- session._session_fields builds a `Fragment(*rows, separator="\n")` instead
  of `mark_safe("\n".join(str(row) ...))` — keeps the tree intact so media
  could bubble, per the Fragment convention.
- Inline SVG icon children use `Safe(...)` nodes instead of `mark_safe(...)`
  strings (filters mode-toggle + collapse icons, date_range_picker calendar
  icon).
- _filter_field reads the widget's own id from its node `.attributes`
  (`_widget_id`) for the label's `for`, dropping the superfluous `for_widget`
  argument that always rendered `for="None"`. Removes the two TODOs whose
  premise ("the Component function can't expose the id") the class/node
  refactor retired, plus RangeSlider's dead commented-out Label block.

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

games/views/session.py

@@ -20,6 +20,7 @@ from common.components import (
     Icon,
     ModuleScript,
     NameWithIcon,
+    Node,
     Popover,
     SearchField,
     SessionDeviceSelector,
@@ -190,13 +191,13 @@ def search_sessions(request: HttpRequest) -> HttpResponse:
     return list_sessions(request, search_string=request.GET.get("search_string", ""))
 
 
-def _session_fields(form) -> SafeText:
+def _session_fields(form) -> Fragment:
     """Manual per-field layout for the session form.
 
     Mirrors the old add_session.html: each field gets its label and widget,
     and the timestamp fields gain a row of now/toggle/copy helper buttons.
     """
-    rows: list[SafeText] = []
+    rows: list[Node] = []
     for field in form:
         children: list[SafeText | str] = [
             mark_safe(str(field.label_tag())),
@@ -234,7 +235,7 @@ def _session_fields(form) -> SafeText:
                 )
             )
         rows.append(Div(children=children))
-    return mark_safe("\n".join(str(row) for row in rows))
+    return Fragment(*rows, separator="\n")
 
 
 @login_required