docs: initialize JamKazam Media Features Modernization

Modernize media opening features (Backing Track, JamTrack, Metronome) from legacy jQuery/Rails to React patterns in jam-ui

Creates PROJECT.md with requirements and constraints.

.planning/config.json

@@ -0,0 +1,10 @@
+{
+  "workflow": {
+    "mode": "interactive",
+    "depth": "standard"
+  },
+  "project": {
+    "name": "JamKazam Media Features Modernization",
+    "initialized": "2026-01-13"
+  }
+}