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/zoned-civil-time.ts

@@ -55,15 +55,12 @@ export function civilDateJsWeekday(isoDate: string): number {
 }
 
 /**
- * Today's civil date (`YYYY-MM-DD`) in an IANA zone.
- *
- * Lets the server derive "today" from a client-supplied time zone instead of trusting a
- * client-supplied date, which matters for relative deadlines like "by Thursday".
+ * Today's civil date (`YYYY-MM-DD`) in an IANA zone, so the server derives "today" from a
+ * client-supplied *zone* rather than trusting a client-supplied date.
  */
 export function civilDateInZone(date: Date, timeZone: string): string {
-  // Intl throws RangeError on an unknown zone, before any fallback below could help, and
-  // this receives a client-supplied string. Callers validate first; this is the backstop
-  // so a bad zone degrades to a date that is at most a day out rather than a 500.
+  // Intl throws RangeError on an unknown zone and this takes a client-supplied string;
+  // callers validate first, this is the backstop.
   const zone = isValidIanaTimeZone(timeZone) ? timeZone : 'UTC';
   const parts = new Intl.DateTimeFormat('en-CA', {
     timeZone: zone,