docs: ARCHITECTURE.md and CHANGELOG.md have no record of competitions, onboarding, or search

[yakew7]

Problem

ARCHITECTURE.md and CHANGELOG.md both predate three major features that have since shipped and been closed out across 15+ issues each: the competitions vertical (#193-#210, #218-#226: schema, browse/detail pages, saves, calendar feed, public API, docs), the onboarding questionnaire (#203-#204), and the site-wide search bar (#222).

CHANGELOG.md has zero mentions of any of it:

$ grep -n "competition\|onboarding\|site search\|nav search" CHANGELOG.md
# (no hits — 250 lines, nothing)

The most recent full entry ([2.4.0]) and the current [Unreleased] section only cover docs/UI polish; none of the competitions/onboarding/search work is recorded anywhere, even though package.json is still at 2.4.0 and all of that work is already merged to main.

ARCHITECTURE.md's route table (under ### src/app/) and its src/components//src/lib/ breakdowns don't mention any of it either — comparing the documented routes against what actually exists in src/app/:

$ find src/app -maxdepth 1 -type d
about account api calendar city competitions contribute docs legal login map offline onboarding

/competitions, /competitions/[slug], /competitions/saved, /city/[slug], /account, /onboarding, /api/places, and /api/competitions are all real, working routes with no row in ARCHITECTURE.md's route table. The src/components/ tree in the same file lists home/, map/, calendar/, pins/, layout/, legal/, docs/, ui/ — but not the competitions/ or onboarding/ component directories, both of which exist and are non-trivial (competitions/ alone has 9 components). The src/lib/ table is missing competitions.ts, competitions-api.ts, competitions-share.ts, competition-events.ts, competition-saves.ts, user-profile.ts, search.ts, docs-nav.ts, docs-meta.ts, ics.ts, jsonld.ts, calendar-feed.ts, and more — most of src/lib/ isn't in the table at all anymore.

Fix

• Add [Unreleased] (or versioned) CHANGELOG.md entries summarizing the competitions vertical, onboarding flow, and site search, since none of it is recorded anywhere.
• Update ARCHITECTURE.md's route table, src/components/ tree, and src/lib/ table to include the routes/components/modules listed above.

Acceptance criteria

• CHANGELOG.md has at least a summary entry for competitions, onboarding, and site search
• ARCHITECTURE.md's route table includes every route currently under src/app/
• ARCHITECTURE.md's component/lib breakdown mentions competitions/ and onboarding/ component directories and the missing src/lib/ modules