feat(filters): replace RangeSlider with Stash-style NumberFilter (#85) (#86)

Numeric range filters could only express BETWEEN/GREATER_THAN/LESS_THAN
via the RangeSlider widget — no way to match NULL/missing values (the
original ask in #32) or exact/not-between. The criteria backend already
supported all 8 numeric modifiers + value2, so this is a UI swap.

- Add NumberFilter component, modeled 1:1 on StringFilter: an 8-modifier
  radio grid plus two number inputs, with the second input revealed only
  for BETWEEN/NOT_BETWEEN and both disabled for IS_NULL/NOT_NULL. Initial
  state is server-rendered so the widget never flashes.
- Migrate all 17 numeric range fields (game/session/purchase/playevent)
  to NumberFilter; drop the now-dead min/max aggregate queries.
- filter-bar.ts: serialize numberFields by modifier (mirroring textFields)
  and wire the modifier radios via event delegation on the persistent
  custom element so they survive htmx swaps of the inner bar body. Apply
  the same delegation fix to the existing string filters.
- Remove RangeSlider entirely: component, range-slider.ts, its custom
  element registration/props, and the range-slider e2e tests.

Backward compatible: old slider filters stored {value, value2, modifier},
the same JSON shape NumberFilter reads, so saved presets keep working.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

e2e/test_widgets_e2e.py

@@ -1,4 +1,4 @@
-"""Browser tests for widget JavaScript (search_select.js, range_slider.js,
+"""Browser tests for widget JavaScript (search_select.js, filter-bar.js,
 add_purchase.js) and their onSwap() initialization lifecycle.
 
 These run a real Chromium via pytest-playwright against pytest-django's
@@ -70,21 +70,21 @@ def test_search_select_adds_include_pill(authenticated_page: Page, live_server):
     expect(pill).to_contain_text("Finished")
 
 
-def test_range_slider_mode_toggle_fires_exactly_once(
+def test_number_filter_between_reveals_second_input(
     authenticated_page: Page, live_server
 ):
-    """One click on the mode toggle flips the slider from range to point mode
-    exactly once. Double-bound listeners (the old force-re-init bug) would
-    flip it twice, leaving data-mode unchanged."""
+    """Selecting the BETWEEN modifier on a NumberFilter reveals its second
+    (value2) input — proof that setupNumberFilters wired the modifier radios on
+    the initial page load."""
     page = authenticated_page
     page.goto(f"{live_server.url}{reverse('games:list_games')}")
     open_filter_bar(page)
 
-    slider = page.locator("range-slider").first
-    expect(slider).to_have_attribute("mode", "range")
+    value2 = page.locator('input[name="filter-year-value2"]')
+    expect(value2).to_be_hidden()
 
-    slider.locator(".range-mode-toggle").click()
-    expect(slider).to_have_attribute("mode", "point")
+    page.locator('input[name="filter-year-modifier"][value="BETWEEN"]').check()
+    expect(value2).to_be_visible()
 
 
 def test_widgets_initialize_inside_htmx_swapped_content(
@@ -94,8 +94,8 @@ def test_widgets_initialize_inside_htmx_swapped_content(
 
     The filter bar is re-fetched and swapped in with htmx.ajax — fresh,
     uninitialized DOM. The swapped-in FilterSelect must open its panel and the
-    swapped-in slider must toggle exactly once, proving the htmx:load half of
-    onSwap and the once-per-element guard."""
+    swapped-in NumberFilter must reveal its second input on BETWEEN, proving the
+    htmx:load half of onSwap and the once-per-element guard."""
     page = authenticated_page
     page.goto(f"{live_server.url}{reverse('games:list_games')}")
 
@@ -111,10 +111,10 @@ def test_widgets_initialize_inside_htmx_swapped_content(
     widget.locator("[data-search-select-search]").click()
     expect(widget.locator("[data-search-select-options]")).to_be_visible()
 
-    slider = page.locator("range-slider").first
-    expect(slider).to_have_attribute("mode", "range")
-    slider.locator(".range-mode-toggle").click()
-    expect(slider).to_have_attribute("mode", "point")
+    value2 = page.locator('input[name="filter-year-value2"]')
+    expect(value2).to_be_hidden()
+    page.locator('input[name="filter-year-modifier"][value="BETWEEN"]').check()
+    expect(value2).to_be_visible()
 
 
 def test_add_purchase_type_toggles_disabled_fields(