feat: spider v6 — 21 curated direct org pages, no Google News

Root cause confirmed: both Google News CBMi links AND Nigerian news
site RSS feeds are inaccessible from GitHub Actions (Cloudflare blocks
Azure datacenter IPs). The only reliable sources are direct org pages
and scholars4dev.com (no Cloudflare).

Changes:
- Removed Google News RSS entirely
- Removed Nigerian news site RSS (blocked from GitHub Actions)
- Expanded direct org list from 8 → 21 pages covering:
    Nigerian govt: PTDF, NDDC, NNPC, SNEPCo, NDIC
    Nigerian corporate: MTN Foundation, Tony Elumelu, Dangote, Access Bank
    International: Commonwealth, Chevening, Fulbright, Mastercard Fn,
                   World Bank (SSL bypass added), AfDB, AU, UNDP,
                   British Council NG, YouthHub Africa, UNICEF, UN
- Added meta['dont_verify_ssl']=True for worldbank.org (TLS hostname
  mismatch on GitHub Actions Azure DNS)
- Kept scholars4dev.com RSS as bonus (accessible, real article URLs)
- open_signals check: skip page if no apply/deadline signals found
- errback writes item with hardcoded apply_link so org is represented
  even if the page is temporarily down

Author: kamsirichard