Keys read as notes on the Plan tile's badge too

The item badge still showed Planning Center's raw "Bb" and "F#m" while the
Song Key tile beside it showed B♭ and F♯m. One module should not spell the
same thing two ways.

The notation moves into key-notation.js and both tiles import it, rather
than each keeping its own copy of the parse: the day one of them changes,
they all should.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

modules/pco-plan/key-notation.js

@@ -0,0 +1,25 @@
+/* PCO Plan — how a song key is written.
+
+   Planning Center stores keys as typed: "Bb", "F#m", "Ab". Every tile in this
+   module shows them as notes instead — B♭, F♯m, A♭ — so the plan, the badge
+   on an item and the Song Key tile all agree. Shared rather than repeated
+   because the day one of them changes, they all should. */
+
+/** "F#m" → { note: 'F', accidental: '♯', quality: 'm' }; anything odd → null. */
+export function parseKey(raw) {
+  const match = /^([A-G])\s*([#b♯♭]?)\s*(.*)$/.exec(String(raw || '').trim());
+  if (!match) return null;
+  const [, note, accidental, quality] = match;
+  return {
+    note,
+    accidental: accidental === '#' ? '♯' : accidental === 'b' ? '♭' : accidental,
+    quality: quality.trim(),
+  };
+}
+
+/** The same thing as one string, for a badge or a caption. */
+export function prettyKey(raw) {
+  const parts = parseKey(raw);
+  if (!parts) return String(raw || '').trim();
+  return `${parts.note}${parts.accidental}${parts.quality}`;
+}