Update validateWikilinks, resolveWikilink, and getBacklinks methods
to use IVaultAdapter and IMetadataCacheAdapter instead of direct App access.
- Implemented inline link suggestion finding using vault adapter
- Implemented backlinks retrieval using metadata cache adapter
- Added helper methods: findLinkSuggestions, extractSnippet, escapeRegex
- App parameter still required for waypoint methods (not in scope for this task)