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/main.ts

@@ -25,9 +25,8 @@ console.log = (...args) => {
 };
 
 async function bootstrap() {
-  // bodyParser is disabled here so the JSON parsers can be registered in an explicit
-  // order below; Nest's built-in one is installed during create() and would otherwise
-  // reject a voice recording at its 100 kb default before any later middleware ran.
+  // bodyParser is disabled so the JSON parsers can be registered in an explicit order below;
+  // Nest's built-in one would otherwise reject a voice recording at 100 kb.
   const app = await NestFactory.create(AppModule, { bodyParser: false });
 
   // Voice needs a larger JSON limit than everything else; see body-parsers.ts.