feat(proxy): nationwide breakwater dataset (249) + /api/breakwaters

User-provided list of 249 breakwaters/landings geocoded via Kakao (keyword
with sigungu matching to avoid same-name mismatches; address/eupmyeon-center
fallback for 13 tiny 리 not in Kakao's DB):
- data/breakwaters.ts: 249 entries {id, name, region, lat, lon, address}.
  강원49 경북75 울산10 부산16 경남22 전남24 전북9 충남10 경기4 인천12 제주18.
- routes/breakwaters.ts: GET /api/breakwaters[?region=]; Breakwater type.

These coordinates feed the existing arbitrary-coordinate tide path, giving a
curated, browseable named-port list like the reference app's 전체지역보기.

Constraint: ~30 entries resolved to eupmyeon-center (approximate, within a few km) — fine for tide timing which uses a 1km grid; exact-precision ones are kakao keyword hits.
Confidence: high
Scope-risk: module
Reversibility: trivial
Directive: Wire into app search (instant local match) + a region-grouped browse list.
Tested: live /api/breakwaters returns 249 with correct per-region counts; coordinates verified in-range via sigungu matching during geocode.
Not-tested: per-breakwater coordinate precision audit (spot-checked only).
Related: docs/BACKLOG.md 0/3-B

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