Gui minor fixes

[qreoct]

• Fixed font styles (bold, italic) not rendering properly on MacOS systems
• Clamped pie chart size so it doesn't get too big/small
• Tweaked sizes of cards to look better on small screens
• Fixed alignment of studied hours on Favourited cards
• Renamed variables for clarity

[codecov-commenter]

Codecov Report

Merging #151 (28d6d34) into master (f59cdd5) will not change coverage. The diff coverage is 0.00%.

@@            Coverage Diff            @@
##             master     #151   +/-   ##
=========================================
  Coverage     59.88%   59.88%           
  Complexity      632      632           
=========================================
  Files            94       94           
  Lines          2518     2518           
  Branches        318      318           
=========================================
  Hits           1508     1508           
  Misses          927      927           
  Partials         83       83           

Impacted Files	Coverage Δ
src/main/java/seedu/address/MainApp.java	0.00% <0.00%> (ø)
src/main/java/seedu/address/ui/InfoDisplay.java	0.00% <0.00%> (ø)
src/main/java/seedu/address/ui/MainWindow.java	0.00% <0.00%> (ø)

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