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, 9 insertions, 0 deletions

diff --git a/internal/slug/slug_test.go b/internal/slug/slug_test.go
index 9953f34..59e2a75 100644
--- a/internal/slug/slug_test.go
+++ b/internal/slug/slug_test.go
@@ -20,6 +20,15 @@ func TestMake(t *testing.T) {
 	}
 }
 
+func TestClean(t *testing.T) {
+	cases := map[string]string{"!!!": "", "": "", "Ντομάτες": "ntomates", "Go ": "go"}
+	for in, want := range cases {
+		if got := Clean(in); got != want {
+			t.Errorf("Clean(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
 func TestValid(t *testing.T) {
 	for _, ok := range []string{"a", "abc-def", "a1-b2"} {
 		if !Valid(ok) {