Bring the architecture doc back up to date with this session's changes

Closes both open "Documentation maintenance" roadmap items. Used a research-only
Explore pass to get a concrete diff against the actual code before editing, rather
than guessing what was stale.

Documented: src/track_layouts_logic.js (previously unmentioned anywhere),
buildEventSchedule, the Settings/Event Manager tab layouts, new state fields
(raceConfig.scheduleStartAt/scheduleGapMin, Session.trackLayoutId, top-level
trackLayouts/audioEventLog), a real SQLite table contract section, a full
field-by-field Settings shape, several previously-undocumented backend routes,
and the complete list of files tests/browser_smoke.js actually invokes.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -8,6 +8,12 @@ The application version is maintained in `package.json` and displayed in the adm
 
 No changes recorded yet.
 
+## 1.20.2 - 2026-09-12
+
+### Changed
+
+- Brought `docs/javascript-architecture.md` back up to date with this session's changes: documented `src/track_layouts_logic.js`, `buildEventSchedule`, the Settings/Event Manager tab layouts, and the new `Event.raceConfig.scheduleStartAt`/`scheduleGapMin` and `Session.trackLayoutId` fields; added a real SQLite table contract section and a full field-by-field `Settings` shape (both previously just TODO notes); documented several previously-undocumented backend routes (`/api/update-status`, `/api/update/run`, `/api/network/public-address`, `/api/passings/purge`, the public-training self-service actions); and listed every file `tests/browser_smoke.js` actually invokes.
+
 ## 1.20.1 - 2026-09-12
 
 ### Changed