creator feedback batch: 9 fixes from initial review

1. About box bg → #0A0C1A (matches icon bg)
2. Elements panel collapses when no element selected / scene changes
3. OpacityChip moved from preview overlay into Elements panel
4. Color picker fix: cast to SceneElement not Source (WebcamSceneConfig was silently blocked)
5. Red left accent bar on selected items in Scene/Source lists
6. ✓ character replaced with Path checkmark icon in Elements panel
7. Removed ToolTip='Applied' from green check buttons
8. Created bugs.md with first entry (iTunes audio on mic meter)
9. Full logo in README + About box uses ytLlive-logo.png

bugs.md

@@ -0,0 +1,9 @@
+# Bugs
+
+## iTunes music showing on mic meter
+Playing music via iTunes causes the mic meter to show audio levels. The WASAPI
+mic capture (`DataFlow.Capture`) and loopback capture (`DataFlow.Loopback`) are
+separate devices. If iTunes audio appears on the mic meter, it is likely acoustic
+coupling — the mic picking up speaker/headphone output. Verify by muting the mic;
+if the meter still shows levels, check Windows Sound settings for stereo mix or
+"listen to this device" routing.