control panel: audio devices, icon font, padding, blur

- audio view: output/input device switching, master volume + mic, and
  per-application streams with their own sliders (pactl sink-inputs)
- icons rendered black because GTK used the desktop font (Noto Sans), which
  has no Nerd Font glyphs; Pango's per-glyph fallback then ignored the css
  colour. Icon classes now name the font explicitly.
- bspwm drew a focus border around the panel that fought the css rounded
  corners: border=off on the rule
- picom now blurs translucent surfaces, so the panel reads as glass rather
  than showing the text behind it
- padding and spacing throughout: frame 20px, section margins, card padding

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cn3dHfbgNYdbZvzb1b3GQt

.config/polybar/config.ini

@@ -36,7 +36,7 @@ module-margin = 0
 modules-left = bspwm
 # modules-center = media-window-toggle
 modules-center = xwindow
-modules-right = cpu sep ram sep gpu sep volume sep time sep control
+modules-right = cpu sep ram sep gpu sep volume sep time
 
 font-0 = JetBrainsMono Nerd Font:style=Bold:pixelsize=10;2
 font-1 = JetBrainsMono Nerd Font:style=Bold:pixelsize=12;2