Better thumbnails & more glacier support

[nl0]

• Thumbnail: skeleton while loading, error / glacier icon if that's the case
• file listing: grey-out archived items
• hide archived / unavailable files from overview and summary where feasible

[codecov-commenter]

Codecov Report

Merging #1796 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1796   +/-   ##
=======================================
  Coverage   88.07%   88.07%           
=======================================
  Files          62       62           
  Lines        6904     6904           
=======================================
  Hits         6081     6081           
  Misses        823      823           

Flag	Coverage Δ
#api-python	85.68% <ø> (ø)
#lambda	92.16% <ø> (ø)

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