fix: restrict RST fields to valid report values

The RST comboboxes allowed free text, so a report typed by hand that isn't in
the mode's list (e.g. "600") was committed. Drop allowFreeText on the four RST
fields (QSO entry + edit modal) and make commit-on-type push a value only when
it's actually in the list; a leftover invalid entry reverts to the last valid
value on blur. Programmatically filled values (FT8 SNR over UDP, presets) are
unaffected — only manual typing is constrained.

frontend/src/components/ui/combobox.tsx

@@ -64,7 +64,17 @@ export function Combobox({
         // Focus selects the text so a keystroke replaces it — but does NOT
         // open the list (so tabbing in doesn't pop the dropdown).
         onFocus={(e) => { setQuery(value); e.currentTarget.select(); }}
-        onChange={(e) => { setQuery(e.target.value); setOpen(true); if (commitOnType) onChange(e.target.value); }}
+        onChange={(e) => {
+          const v = e.target.value;
+          setQuery(v);
+          setOpen(true);
+          // Commit-on-type pushes the value live to the parent (so a CW macro sent
+          // without leaving the field uses what was just typed). With free text that's
+          // any input; a restricted field (allowFreeText=false) commits ONLY a value
+          // that's actually in the list, so a half-typed or invalid report never
+          // becomes the committed value — blur then reverts the leftover text.
+          if (commitOnType && (allowFreeText || options.some((o) => o.toLowerCase() === v.trim().toLowerCase()))) onChange(v);
+        }}
         onBlur={onBlur}
         onKeyDown={(e) => {
           if ((e.key === 'ArrowDown' || e.key === 'Alt') && !open) { setOpen(true); }