SRVOCF-850: Editor Page layout and UX improvements

[Cragsmann]

Summary

Improves the editor page layout and adds visual context for the function being edited.

• Replace hardcoded Flex layout (fixed 16rem sidebar) with PatternFly Sidebar/SidebarPanel/SidebarContent for responsive 25% panel width
• Add info bar between toolbar and editor showing function name and a link to the GitHub repo
• Add FolderIcon/FolderOpenIcon to directory nodes in the file tree

Changes

• 🧹 FunctionEditPage.tsx: swap Flex/FlexItem for Sidebar/SidebarPanel/SidebarContent, add Content info bar with repo metadata
• 🧹 FileTreeView.tsx: add FolderIcon/FolderOpenIcon from @patternfly/react-icons to directory tree nodes
• ✅ FunctionEditPage.test.tsx: add test for info bar rendering with repo link
• ✅ FileTreeView.test.tsx: add test for folder icon presence on directories (and absence on files)

Relates to SRVOCF-850

[dsimansk]

@Cragsmann any screenshots?