fix: Port upstream 1.1.0-rc PRs #1014, #1018, #990 and align #1002

Port three new upstream commits and align the existing #1002 port:

- PR #1014: Strip unused CSS rules by filtering unsupported selector
  types (+, >, [, :, #, ~, *, descendants) in processRuleBlockWithStyle.
  Fix normalized() trailing whitespace to also strip newlines.
- PR #1018: Add deleteCache() to CssParser, move CSS_CACHE_VERSION to
  static class member, remove stale cache on version mismatch, invalidate
  section caches (Storage.removeDir) when CSS is rebuilt. Refactor
  parseCssFiles() to early-return when cache exists.
- PR #990: Adapt classic theme continue-reading card width to cover
  aspect ratio (clamped to 90% screen width), increase homeTopPadding
  20->40, fix centering with rect.x offset for boxX/continueBoxX.
- #1002 alignment: Add tryInterpretLength() to skip non-numeric CSS
  values (auto, inherit), add "both width and height set" image sizing
  branch in ChapterHtmlSlimParser.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/components/themes/BaseTheme.h

@@ -82,7 +82,7 @@ constexpr ThemeMetrics values = {.batteryWidth = 15,
                                  .tabBarHeight = 50,
                                  .scrollBarWidth = 4,
                                  .scrollBarRightOffset = 5,
-                                 .homeTopPadding = 20,
+                                 .homeTopPadding = 40,
                                  .homeCoverHeight = 400,
                                  .homeCoverTileHeight = 400,
                                  .homeRecentBooksCount = 1,