docs(6208): the remaining frontend comments drop milestone, step and rule citations

Components, stores, api clients, router, types and shared CSS now state what
each piece is and why, without the milestone that introduced it. diff.ts
names its consumers instead of the copy history; stores/notes and tasks state
their current scope instead of the cleanup that set it; theme.css states the
token practice instead of the sweep that established it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/components/BackupScheduleSettings.vue

@@ -11,7 +11,7 @@ import { fmtStamp } from "@/utils/dateFormat";
 import { useToastStore } from "@/stores/toast";
 
 /**
- * Scheduled backups (milestone 523): one dated, uncompressed tar per run,
+ * Scheduled backups: one dated, uncompressed tar per run,
  * delivered to a folder or an S3 bucket. The page answers "is my data backed
  * up?" first — the verdict, then anything wrong — and the settings follow.
  */
@@ -50,7 +50,7 @@ async function load() {
   }
 }
 
-// While a backup runs, follow it. Re-armed from load()'s finally (rule 157),
+// While a backup runs, follow it. Re-armed from load()'s finally, never after the work,
 // so one failed read does not stop the page following the run.
 function schedulePoll() {
   if (pollTimer) clearTimeout(pollTimer);