fix: deduplicate crawled URLs, fix -m flag collision, add elapsed time + userAgent support

[VaishnavGunjari]

What's changed

Bug fixes

• Duplicate -m CLI flag: Both --match and --maxPagesToCrawl were registered with the same -m shorthand, causing silent option shadowing. Fixed by changing --maxPagesToCrawl to -n.
• Typo in variable name RESOURCE_EXCLUSTIONS → RESOURCE_EXCLUSIONS (affected all 3 usages).

Improvements

• URL deduplication: Added a seenUrls Set to skip already-visited URLs during a crawl, preventing duplicate entries in the output and wasted requests.
• Elapsed-time logging: A summary line (✅ Crawl complete: N page(s) crawled in Xs) is printed when the crawl finishes.
• Custom userAgent config option: Users can now set a userAgent string in config.ts to override the default Playwright User-Agent on every request.

No breaking changes

All changes are backward-compatible. New config fields are optional.