Remove inline-handler → window.* contract (issue #28)

Finish the behavioural refactor from #28: no first-party JS lives on the
global object solely to be reachable from a server-rendered inline on*
attribute, and no inline Alpine blobs remain in the filter bar / year picker.

- Filter-bar collapse: drop the inline onclick for a delegated click listener
  on the persistent <filter-bar> custom element (data-filter-bar-toggle). The
  inner #filter-bar body is htmx-swapped while connectedCallback does not re-run,
  so delegation on the host preserves the swap-survival the inline handler had.
- YearPicker: convert the Alpine x-data/x-on/x-ref/_pickerInstance f-string into
  a <year-picker> custom element with typed props (YearPickerProps). Behavior
  moves to ts/elements/year-picker.ts; ts/year_picker.ts and _YEAR_PICKER_MEDIA
  are removed. The builder lives in primitives.py (next to YearPicker) to avoid a
  circular import; registration stays in custom_elements.py for codegen.
- Add bindPopupDismiss (ts/utils.ts): shared Escape + outside-click dismiss with
  a cleanup return and an extraInside hook for popups mounted on document.body.
  Adopted by date-range-picker.ts (1:1) and year-picker.ts (Datepicker popup is
  body-mounted, passed as an extra inside root).

Follow-up #49 tracks unifying popup/dismiss/positioning across the remaining
dropdown/search-select/Flowbite cases.

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

common/components/filters.py

@@ -563,10 +563,8 @@ def _filter_collapse_button() -> Node:
             ("type", "button"),
             # Slider handles are positioned in percentages, so initializing
             # them while the body is hidden is safe — no re-init on reveal.
-            (
-                "onclick",
-                "document.getElementById('filter-bar-body').classList.toggle('hidden')",
-            ),
+            # Click is wired by filter-bar.ts (no inline handler).
+            ("data-filter-bar-toggle", ""),
             (
                 "class",
                 "flex items-center gap-2 text-sm font-medium text-body "