caldata: allow an external universal sanctorale to override the embedded one

The universal calendar of saints can now be refreshed or replaced without a
rebuild: if ~/.config/lectio/sanctorale/of.ini (OF) or ef.ini (EF) is present
and parses, caldata.Base uses it instead of the embedded calendar; a missing or
malformed file falls back to the embedded default, so the binary stays
self-contained and correct out of the box. Local diocesan/national additions
keep layering on top via calendars/ + `use` (unchanged). The temporal cycle and
precedence rules stay in code -- only the sanctorale is data.

- caldata.SetSanctoraleDir hook (mirrors bible/naming/i18n); Base() prefers the
  external file per form. config.SanctoraleDir(); wired in the CLI, TUI and web
  entry points. Tests cover override, no-file, and malformed-file fallback.
- README: new "Calendar of saints" section (two tiers: overlay via `use`,
  replace via sanctorale/<form>.ini); config comment notes the override.

1 files changed, 4 insertions, 0 deletions

diff --git a/internal/cli/cli.go b/internal/cli/cli.go
index 16ba753..c0c9dea 100644
--- a/internal/cli/cli.go
+++ b/internal/cli/cli.go
@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/lukaszkasprzak/lectio/internal/bible"
+	"github.com/lukaszkasprzak/lectio/internal/caldata"
 	"github.com/lukaszkasprzak/lectio/internal/config"
 	"github.com/lukaszkasprzak/lectio/internal/export"
 	"github.com/lukaszkasprzak/lectio/internal/i18n"
@@ -210,6 +211,9 @@ func Run(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 	if dir, err := config.UIDir(); err == nil {
 		i18n.SetUserDir(dir)
 	}
+	if dir, err := config.SanctoraleDir(); err == nil {
+		caldata.SetSanctoraleDir(dir)
+	}
 	if lectionary != "" {
 		cfg.Lectionary = lectionary
 	}