docs: cut the comments that were not earning their place

I wrote 731 comment lines on this branch against 4,530 lines of code — 14%,
where the rest of the repo runs at 1.8%. CLAUDE.md asks for code that reads
like its surroundings, and this did not.

Removed by genre rather than by taste:

- restating the code, e.g. "JS getUTCDay() numbering: Sunday = 0" above the
  map that literally shows it, and a docblock on startOfWeek explaining that
  it returns the start of the week;
- narrating history — "this used to rebuild the whole map", "left the bar
  recording forever" — which the commit message and git blame already carry;
- saying the same thing in several places: the "cannot record is not a
  denied microphone" reason appeared three times in one file, and the
  "aborting stops a per-minute metered call" reason across three files. Each
  now lives once, where the behaviour it explains lives;
- defending decisions nobody would question, like why toLatinDigits is its
  own module;
- over-explaining defensive branches, three separate comments to distinguish
  null from missing-kind from unrecognised-kind.

What stays is what the code cannot say: the patient-right convention in
toFdi, whose failure mode is a valid code for the wrong tooth; the
"this"-vs-"next" week anchoring; StrictMode re-arming mountedRef; Safari
accepting no mimeType hint; and the invariants whose violation already cost
a bug — the body parser's middleware ordering and the dispatch panel's
auto-fill rules.

Comments only. The diff contains no non-comment line.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

backend/src/common/body-parsers.ts

@@ -17,23 +17,18 @@ export const VOICE_BODY_LIMIT = '10mb';
  * of audio, so that one route needs a larger limit while every other endpoint keeps the
  * default — a large body should not become acceptable everywhere.
  *
- * Deliberately a single middleware that *chooses* a parser, rather than a path-mounted
- * parser stacked in front of a default one. That arrangement relied on Express's
- * mount-path stripping plus body-parser skipping an already-parsed request, and it
- * silently stopped applying when the surrounding middleware order shifted — at which point
- * the endpoint rejected every real recording with a 500. One explicit branch has no such
- * coupling, and is covered by body-parsers.spec.ts.
+ * Deliberately one middleware that *chooses* a parser, not a path-mounted parser stacked in
+ * front of a default one: that arrangement depended on Express's mount-path stripping and on
+ * body-parser skipping an already-parsed request, and silently stopped applying whenever the
+ * middleware order shifted. One explicit branch has no such coupling.
  */
 /**
- * Express routes case-insensitively and ignores a trailing slash unless configured
- * otherwise, so `/API/Voice/Extract/` reaches the same controller. Matching only the
- * canonical spelling would hand those requests the 100 kb parser and 413 every real
- * recording — a failure that looks like a broken microphone, not a routing detail.
+ * Express routes case-insensitively and ignores exactly one trailing slash, so
+ * `/API/Voice/Extract/` reaches the same controller and must get the same limit — otherwise
+ * it 413s every real recording, which reads as a broken microphone rather than a route.
+ * Two slashes never route, so they must not buy a 10 MB buffer either.
  */
 function isVoiceExtractPath(path: string): boolean {
-  // Exactly one trailing slash, because that is exactly what Express ignores. Stripping
-  // every trailing slash would hand the 10 MB parser to `/api/voice/extract//`, which
-  // buffers the body and then 404s — memory spent on a request that never routes.
   return path.toLowerCase().replace(/\/$/, '') === VOICE_EXTRACT_PATH;
 }