Convert date_range_picker.js to TypeScript (issue #17)

- Add ts/date_range_picker.ts: typed port. CalendarState interface (with the
  dynamically-assigned refreshFromField) and an Anchor union replace the loose
  state object; date helpers and DOM queries fully typed; var → const/let
- Replace the DOMContentLoaded + per-element guard-flag + window global with
  onSwap("[data-date-range-picker]", ...), the documented init pattern — so the
  picker now also initializes inside htmx-swapped fragments. Drops the dead
  window.initDateRangePickers export
- Point the DateRangePicker component Media at dist/date_range_picker.js and load
  it as an ES module in the e2e page (was a deferred classic script)

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

common/components/date_range_picker.py

@@ -12,17 +12,17 @@
 
 The committed value lives in two hidden ISO-date inputs named
 ``{input_name_prefix}-min`` / ``{input_name_prefix}-max`` — the same contract
-as the older ``DateRangeFilter``, so ``filter_bar.js`` serializes either
+as the older ``DateRangeFilter``, so ``filter_bar.ts`` serializes either
 widget into a ``DateCriterion`` unchanged. All behaviour is wired by
-``games/static/js/date_range_picker.js``.
+``ts/date_range_picker.ts`` (compiled to ``dist/date_range_picker.js``).
 """
 
 from common.components.core import Element, HTMLAttribute, Media, Node, Safe
 from common.components.primitives import Div, Input, Span
 from common.time import DatePartSpec, date_parts
 
-# Wired by date_range_picker.js.
-_DATE_RANGE_MEDIA = Media(js=("date_range_picker.js",))
+# Wired by ts/date_range_picker.ts (compiled to dist/).
+_DATE_RANGE_MEDIA = Media(js=("dist/date_range_picker.js",))
 
 _FIELD_CONTAINER_CLASS = (
     "flex items-center gap-0.5 w-full rounded-base border border-default-medium "