Stop finance readers borrowing data from skipped club records; release 0.5.10

[rhiever]

Summary

• The club scan skips some club records, such as clubs playing in another nation's league. A skipped record's finance series, sponsors and facilities were read under the accepted club stored before it.
• finances(), sponsorships() and facilities() now end each club's span at the next record header, accepted or not. The club index, clubs(), staff and every other reader keep their spans unchanged.
• The header search costs 1 to 3 s per save. It runs once, and only for those 3 readers.
• Release 0.5.10.

Refs #20

Verification

• Before and after runs on 48 local saves (network denied, checksums unchanged): 15 saves lose rows that belonged to skipped records. No rows are added, and no other reader's output or checks change. The issue FM26 build 26.3.2: players export fails with name pools not found #20 save's finances() goes from failed (finance_clubs_with_two_chains = 2) to ok.
• New unit tests cover skipped records between and after accepted ones, plus bytes that only look like a header. The finance test fails on main.
• ruff, pyright, unit tests and local corpus tests pass.

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