Stamp each source's registry added date; date the v0.2.0 sources 2026-06-15 (v2#80) (#97)

studia_bas: record the licence notices of the 17 issue PDFs (v2#79) (#90)

studia_bas: licence version resolved to CC BY 3.0 PL (evidence + tests, no data change) (#80)

studia_bas: Studia BAS policy articles (scoped from #19) (#44)