Add post tags, with a tag page and two side-column modules

Posts can now carry tags, set on the post form as a checklist of the
blog's existing tags plus a comma-separated box for new ones (no JS).
A tag is a name and a unique slug, so "Go" and "go" are one tag and
Greek tags get readable URLs; tags no post uses any more are deleted.

On the blog, tags appear under the post date and link to /tag/<slug>,
which lists the published posts from every page, paginated like a page.
Two new layout modules show them: a Tags list (with counts, by use) and
a Tag cloud (alphabetical, sized by use). Both are only fetched when a
visible module needs them.

The article loop and pager move to a shared postlist partial; while
there, the pager stops adding a trailing slash — /news/?p=2 was a 404
because a {page} wildcard never matches one.

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

1 files changed, 29 insertions, 12 deletions

diff --git a/internal/web/layout.go b/internal/web/layout.go
index ad55e82..b8069a0 100644
--- a/internal/web/layout.go
+++ b/internal/web/layout.go
@@ -13,8 +13,8 @@ import (
 // blocks; the side columns take the small boxes; the footer its own set.
 var moduleKinds = map[string][]string{
 	"header": {"title", "logo", "menu"},
-	"left":   {"menu", "recent", "archive", "logo", "html"},
-	"right":  {"menu", "recent", "archive", "logo", "html"},
+	"left":   {"menu", "recent", "archive", "tags", "tagcloud", "logo", "html"},
+	"right":  {"menu", "recent", "archive", "tags", "tagcloud", "logo", "html"},
 	"above":  {"html"},
 	"below":  {"html"},
 	"footer": {"text", "rss", "sitemap", "html"},
@@ -22,15 +22,17 @@ var moduleKinds = map[string][]string{
 
 // Friendly names for the dashboard (English; translate with t / s.tr at the point of use).
 var moduleNames = map[string]string{
-	"title":   "Blog title & tagline",
-	"logo":    "Logo",
-	"menu":    "Menu",
-	"archive": "Archive (posts by month)",
-	"recent":  "Recent posts",
-	"html":    "Custom HTML",
-	"rss":     "RSS link",
-	"text":    "Footer text",
-	"sitemap": "Site map",
+	"title":    "Blog title & tagline",
+	"logo":     "Logo",
+	"menu":     "Menu",
+	"archive":  "Archive (posts by month)",
+	"recent":   "Recent posts",
+	"tags":     "Tags",
+	"tagcloud": "Tag cloud",
+	"html":     "Custom HTML",
+	"rss":      "RSS link",
+	"text":     "Footer text",
+	"sitemap":  "Site map",
 }
 
 var areaNames = map[string]string{
@@ -53,7 +55,7 @@ func allowedKind(area, kind string) bool {
 // moduleHasSettings says whether the module has an edit page.
 func moduleHasSettings(kind string) bool {
 	switch kind {
-	case "html", "text", "recent", "archive", "sitemap":
+	case "html", "text", "recent", "archive", "sitemap", "tags", "tagcloud":
 		return true
 	}
 	return false
@@ -64,6 +66,11 @@ func moduleSummary(lang string, m store.Module) string {
 	switch m.Kind {
 	case "recent":
 		return i18n.Tf(lang, "%d posts", m.Count) + headingNote(lang, m)
+	case "tags":
+		if m.Count == 0 {
+			return i18n.T(lang, "all tags") + headingNote(lang, m)
+		}
+		return i18n.Tf(lang, "%d tags", m.Count) + headingNote(lang, m)
 	case "html", "text":
 		body := strings.Join(strings.Fields(m.Body), " ")
 		if body == "" {
@@ -160,6 +167,16 @@ func (l Layout) NeedsArchive() bool {
 	return false
 }
 
+// NeedsTags says whether any visible module shows the tags.
+func (l Layout) NeedsTags() bool {
+	for _, m := range l.all() {
+		if m.Kind == "tags" || m.Kind == "tagcloud" {
+			return true
+		}
+	}
+	return false
+}
+
 // MaxRecent is the longest "recent posts" list any visible module wants (0 = none).
 func (l Layout) MaxRecent() int {
 	n := 0