Increase contrast of Solarized Light in Web IDE

Problem to solve

As described in #300322 (closed), the Solarized Light theme lacks sufficient contrast between the file tree and code area.

Proposal

Update the Solarized Light theme to use:

• --ide-background: #DDD6C1
• --ide-highlight-background: #EEE8D5
• --ide-background-hover: #D3CBB7
• --ide-border-color:#DED7C1

Current	Proposal