feat(polish): close all 6 review nitpicks in one sweep

closes board-viewer-polish

- M1 src/parser.ts: comment explaining why **Status:** text field is intentionally
  ignored (emoji is canonical, prevents future-reader head-scratch)
- M2 src/render.ts + tests: clamp future ISO to '0m' (server clock drift safety)
  + inline comment + test
- M3 .tasks/board-viewer-gitea-reader.md: decisions-log clarifying orphan
  per-task files are out of scope by design (STATUS.md = index of record)
- M4 static/board.{js,css} + src/render.ts: filter rebuilt to query records
  (not DOM badge text); 5 status-filter pill buttons in header with active
  toggle state; smoke-verified blocked filter
- M5 deploy/Dockerfile.build: HEALTHCHECK (file fresher than 2×tick) and
  stderr redirect for failures with timestamp
- M6 src/reader.ts: parallelize getLatestCommitIso per-repo via Promise.all
  (preserves block order)

49 tests pass (was 43 pre-polish), typecheck clean, smoke against real Gitea
returns 81 records from 4 repos.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.tasks/board-viewer-polish.md

@@ -48,12 +48,12 @@ Bundle of minor / nitpick findings from `board-viewer-review` checkpoint. Each
 
 ## Completed steps
 
-- [ ] M1: parser comment
-- [ ] M2: formatAge future-ts test + comment
-- [ ] M3: decisions-log entry in gitea-reader.md
-- [ ] M4: filter rebuild + status multi-select OR acceptance amendment
-- [ ] M5: stderr + Docker HEALTHCHECK
-- [ ] M6: parallelize commit-iso fetches
+- [x] M1: comment в `parser.ts` объясняющий что `**Status:**` text field intentionally ignored (emoji canonical)
+- [x] M2: тест clamps future timestamps to "0m" + inline comment в formatAge
+- [x] M3: decisions-log entry в gitea-reader.md: orphan per-task без блока в STATUS.md — out of scope by design
+- [x] M4: filter rebuilt to query underlying records (status always known); 5 status-filter pill buttons добавлены в header; click toggles active set; CSS `.status-filter.active` filled. Smoke-verified: click "blocked" → только 1 blocked задача видна.
+- [x] M5: HEALTHCHECK в Dockerfile.build (index.html exists AND fresher than 2×tick); failures redirected to stderr с timestamp
+- [x] M6: `getLatestCommitIso` parallelized via Promise.all per-repo (preserves block order)
 
 ## Notes