refactor: remove the niedziela/missalemeum scrapers, bt, traditional_lang

The daily view now computes entirely offline (previous commit), so retire the
network path and everything that served it:

- Delete internal/tradlit (missalemeum) and the niedziela scraper from
  internal/liturgy (fetch/store/parse + fixtures); keep Section, DayInfo and
  ExtractCitation.
- Remove the "bt" version everywhere (render gatherBT + branches, config,
  i18n, web form, TUI) and bible.ToEnglishRef (Polish citation converter).
  A legacy config carrying "bt" migrates to "wuj" on load (config.migrateBT).
- Remove the traditional_lang config field and the -g/--lang flag from all
  three binaries.
- Drop the now-dead flags -R/--refresh, -o/--offline, -u/--update,
  -C/--clean and the harvest/clean commands.
- New defaults: versions = wuj,vul,grb,drb; default_version = vul.

Update the README (offline-by-design, no harvest/update), help text, and
stale niedziela/bt doc comments. Tests updated for the offline reality;
go test ./... and go vet ./... are clean, all three binaries build and run
offline (OF + EF, compare, web).

1 files changed, 21 insertions, 0 deletions

diff --git a/internal/liturgy/citation.go b/internal/liturgy/citation.go
new file mode 100644
index 0000000..2c545c2
--- /dev/null
+++ b/internal/liturgy/citation.go
@@ -0,0 +1,21 @@
+package liturgy
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// citationRe captures a scripture reference in a trailing "(...)" of a section
+// heading, e.g. "Ewangelia (J 20, 1. 11-18)" -> "J 20, 1. 11-18".
+var citationRe = regexp.MustCompile(`\((.+)\)\s*$`)
+
+// ExtractCitation returns the scripture reference carried in a section
+// heading's trailing parentheses, or an error when the heading has none.
+func ExtractCitation(heading string) (string, error) {
+	m := citationRe.FindStringSubmatch(heading)
+	if m == nil {
+		return "", fmt.Errorf("no reference found in heading: %q", heading)
+	}
+	return strings.TrimSpace(m[1]), nil
+}