feat: strict remote-only filtering with positive remote evidence

LinkedIn's f_WT=2 filter is nearly ignored for guest scraping and guest
pages expose no structured workplace-type field, so text filtering is
the only option:

- Require positive remote evidence (title/location/description must say
  remote) before keeping a job; silence now means drop, not keep.
  Configurable via scraper.require_remote_evidence.
- Catch more hybrid/on-site phrasings: "Hybrid: <city>", "office-based",
  "N days onsite/in office", "return to office", titles with
  hybrid/onsite (without tripping on "hybrid cloud").
- Append "Remote" to search keywords when remote_only is on, since
  keyword matching surfaces far more genuinely remote posts than the
  broken filter.

Verified against live LinkedIn postings: three known hybrid/on-site
leaks dropped, known remote post kept.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

config.yaml

@@ -49,6 +49,11 @@ scraper:
   location: "Canada"
   work_types: ["remote"]
   remote_only: true   # also drop jobs whose location/description reveals hybrid or on-site
+  # LinkedIn's remote filter is unreliable for logged-out scraping, so on top of
+  # dropping visible hybrid/on-site jobs, require positive proof of remote
+  # (title/location/description must say remote). Strict: jobs that never state
+  # they're remote are dropped. Set false to keep unverified jobs.
+  require_remote_evidence: true
   pages_per_keyword: 3
   delay_between_pages: [3, 6]
   delay_between_keywords: [5, 10]