feat: add jurisdiction field to rules, facts and extraction

Rule now carries a required Jurisdiction (land) field, and Facts a
matching Jurisdiction supplied by the caller (like Platform — no
legal jurisdiction can be read off a caption or image, so the model
never guesses it). Evaluate() only lets a rule fire when its
jurisdiction matches the facts' jurisdiction.

This is the structural half of "deutsche Rechtslage zuerst, Struktur
für Österreich und Schweiz vorgesehen": a future AT/CH rule set can be
added as plain new YAML files without touching existing DE rules, but
no AT/CH content is added now — that needs its own legal research
first, same as WK-001/WK-004 needed for Germany.

WK-001 and WK-004 are tagged land: DE, all golden fixtures carry
jurisdiction: DE, and extract.Input passes Jurisdiction through
unchanged into the returned Facts.

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

rules/WK-001.yaml

@@ -1,5 +1,6 @@
 id: WK-001
 version: 1
+land: DE
 titel: Keine Kennzeichnung trotz Gegenleistung
 bedingung:
   gegenleistung: [bezahlt, sachbezug]

rules/WK-004.yaml

@@ -1,5 +1,6 @@
 id: WK-004
 version: 1
+land: DE
 titel: Kennzeichnung nicht auf den ersten Blick erkennbar (Kürzung durch "mehr anzeigen")
 bedingung:
   gegenleistung: [bezahlt, sachbezug]