Add languages: English and Greek, chosen per blog on the Settings tab

Every blog and its dashboard were hard-wired to English. A blogger can
now pick the language of their blog; it switches the whole dashboard and
the blog's fixed text — post dates, archive months, the RSS link, the
pager, the 404 page — while what the blogger wrote is left alone.

The new internal/i18n package keys translations by the English string,
so an untranslated key renders as English rather than blank, and
TestGreekCatalogComplete scans the templates and handlers to fail when
the Greek catalog misses a key or keeps a stale one. Templates are
compiled once per language with t/tf/date/postdate/month closed over the
language, so they need no data plumbing.

The language lives in settings.language (blog migration 00002), not in
the theme, so "Reset design" does not touch it. Public pages use the
blog's language; management pages use the logged-in user's own blog's,
so a superadmin editing someone else's blog keeps theirs; the login page
follows Accept-Language.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sd8UPWrvyYCLj97JexNw3A

1 files changed, 1 insertions, 13 deletions

diff --git a/internal/web/theme.go b/internal/web/theme.go
index 1ecd832..2853667 100644
--- a/internal/web/theme.go
+++ b/internal/web/theme.go
@@ -8,7 +8,6 @@ import (
 	"strconv"
 	"strings"
 	"text/template"
-	"time"
 
 	"github.com/google/uuid"
 )
@@ -43,7 +42,7 @@ type Theme struct {
 	NavHover string `json:"nav_hover"` // "" = same as NavText
 
 	ShowDates  bool   `json:"show_dates"`
-	DateFormat string `json:"date_format"` // long | short | iso
+	DateFormat string `json:"date_format"` // long | short | iso (rendered by i18n.FormatDate)
 
 	FooterBg    string `json:"footer_bg"`
 	FooterColor string `json:"footer_color"`
@@ -283,17 +282,6 @@ func (t Theme) JSON() json.RawMessage {
 	return b
 }
 
-// FormatDate renders post dates in the blogger's chosen style.
-func (t Theme) FormatDate(at time.Time) string {
-	switch t.DateFormat {
-	case "short":
-		return at.Format("2 Jan 2006")
-	case "iso":
-		return at.Format("2006-01-02")
-	}
-	return at.Format("2 January 2006")
-}
-
 // ---- presets ----------------------------------------------------------------
 
 // Preset is a named colour scheme; applying one touches only colours.