test: badge E2E tests — fix __version wipe, extract idb_helpers, add render + workflow tests

Root cause fix: tests/_helpers/ae_defaults.ts was missing __version: 1, causing
store_versions.ts to wipe ae_loc from localStorage on every test page load. This
made trusted_access fall back to false, hiding the print button (can_print guard)
and failing all attendee workflow tests.

Changes:
- ae_defaults.ts: add __version: 1 with comment explaining the store_versions guard
- idb_helpers.ts: extract inject_badge_and_template() from print layout test into
  shared helper; now used by all three print/render test files
- event_badge_render.test.ts: new — 4 tests covering full_name_override priority,
  full_name fallback, duplex=0 hides badge back, duplex=1 shows badge back
- event_badge_attendee_workflow.test.ts: cleaned up (diagnostic code removed);
  all 3 tests now pass
- event_badge_print_layout.test.ts: renamed from badge_print_layout.test.ts;
  inline inject_idb() replaced with shared idb_helpers import
- event_badge_smoke.test.ts: renamed from event_badge.test.ts
- playwright.config.ts: use system /usr/bin/chromium on Arch Linux (avoids
  Playwright's bundled Chromium which requires Ubuntu libs not present on Arch)

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

tests/_helpers/ae_defaults.ts

@@ -1,4 +1,5 @@
 export const ae_app_local_data_defaults = {
+    __version: 1, // Must match AE_LOC_VERSION in src/lib/stores/store_versions.ts — store_versions.ts wipes ae_loc if version doesn't match
     last_page_reload: null,
     last_cache_refresh: Date.now(),
     cache_expired: false,