kiosk: chromium 72 mime + flex-gap fixes

Pi's onboard chromium is 72 (Jan 2019). Two issues:

1. Python 3.5's mimetypes doesn't know woff/woff2/ttf, so Tornado
   serves them as application/octet-stream which chromium 72 refuses
   to use as web fonts -> all FA6 icons render as empty boxes. Add
   scripts/deploy/patch_font_mime.py that monkey-patches bbctrl
   Web.py's StaticFileHandler with correct content types. Run
   automatically by deploy-hardware.sh (idempotent).

2. flex-gap landed in chromium 84. Add '> * + *' margin fallbacks
   for the flex containers that show up on Program tab (action-bar,
   action-btn, file-bar, file-btn) and tighten the kiosk-mode
   settings rail so all 14 items fit in 768px height.

src/stylus/style.styl

@@ -2570,3 +2570,51 @@ html.kiosk-mode
   .control-page .jog-head > * + *
     margin-left 8px
 
+
+  // Settings rail must be scrollable in kiosk mode \u2014 the 14+
+  // item list overflows the 768px viewport at default heights.
+  .settings-shell
+    grid-template-columns 220px 1fr
+    gap 10px
+
+  .settings-rail
+    position static
+    align-self stretch
+    max-height 100%
+    overflow-y auto
+
+  .settings-rail .set-item
+    height 36px
+    font-size 0.85rem
+    padding 0 10px
+
+    .fa
+      width 14px
+      font-size 0.9rem
+
+  .settings-rail .set-section
+    margin 6px 4px 2px
+    font-size 0.62rem
+
+  .settings-rail .set-rail-foot
+    margin-top 4px
+    padding-top 6px
+
+    .sp-shutdown, .sp-save
+      height 32px
+      font-size 0.85rem
+
+
+// Program tab flex-gap fallbacks for Chromium 72.
+// Action bar (RUN/STOP/UPLOAD/.../DELETE) and the action buttons
+// themselves (icon stacked over label).
+.action-bar > * + *
+  margin-left 12px
+.action-btn > * + *
+  margin-top 4px
+
+// File bar (Create Folder / folder select / file select / sort).
+.file-bar > * + *
+  margin-left 10px
+.file-btn > * + *
+  margin-left 0.4rem