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>

README.md

@@ -357,10 +357,14 @@ below. Nothing is installed without someone clicking.
   explain.
 
   **Song Key** is one value, as large as the tile allows: the key of the item
-  ProPresenter has live, set as a note (B♭, F♯m), with the song's name and the
-  next key under it — both switches, as is the colour. When the feed that
-  picks the item is gone the key stays up, faded, and the tile's dot says so
-  rather than pretending to be current.
+  ProPresenter has live, with the song's name and the next key under it — both
+  switches, as is the colour. When the feed that picks the item is gone the key
+  stays up, faded, and the tile's dot says so rather than pretending to be
+  current.
+
+  Keys are written as notes wherever the module shows one: Planning Center's
+  `Bb` and `F#m` read as B♭ and F♯m, on the Plan tile's item badge and in the
+  Song Key tile alike.
 
   **Teams** shows the same plan's team and position assignments — each team
   as a band of its people, with their photo (fetched through ProdDash, never