web: HTMX server + lectio-web binary

NewServer wires B1's RenderReadings/Themes/themeCSS/embedded static+
templates FS into an http.ServeMux: GET / (full page), GET /readings
(HTMX reading-pane fragment), GET /lookup (bible.Lookup passage search
fragment), GET /theme.css (theme stylesheet, falling back through
cfg.WebTheme to the built-in default on an unknown name), GET /static/.
Run listens on cfg.WebPort (0 = OS-picked free port), prints the URL,
best-effort opens a browser, then serves. cmd/lectio-web is the binary
entry point (config.Load -> web.Run).

Fold-in from the B1 review: hardened themeCSS's name guard to an
explicit ^[A-Za-z0-9_-]+$ allowlist (the old filepath.Base/ContainsAny
check let ".." through), plus guard-rejection and HTML-escaping
regression tests -- B2 is what makes /theme.css?name=<raw> reachable
from the network, so it owns closing this out.

1 files changed, 24 insertions, 0 deletions

diff --git a/internal/web/render_test.go b/internal/web/render_test.go
index c42e1b1..87ee62d 100644
--- a/internal/web/render_test.go
+++ b/internal/web/render_test.go
@@ -30,6 +30,30 @@ func TestBuiltinThemes(t *testing.T) {
 	}
 }
 
+func TestThemeCSSGuardRejectsInvalidNames(t *testing.T) {
+	t.Setenv("XDG_CONFIG_HOME", t.TempDir()) // no user themes
+	for _, name := range []string{"../../etc/passwd", "..", "a/b", ""} {
+		if _, err := themeCSS(name); err == nil {
+			t.Errorf("themeCSS(%q): expected error, got nil", name)
+		}
+	}
+}
+
+func TestRenderReadingsEscapesScriptText(t *testing.T) {
+	secs := []liturgy.Section{{
+		Heading:    "Test",
+		PartID:     "pierwsze_czytanie",
+		Paragraphs: [][]string{{"<script>alert(1)</script>"}},
+	}}
+	html := string(RenderReadings(secs, []string{"pl"}, "new"))
+	if strings.Contains(html, "<script>alert(1)</script>") {
+		t.Errorf("raw <script> leaked into rendered output: %q", html)
+	}
+	if !strings.Contains(html, "&lt;script&gt;alert(1)&lt;/script&gt;") {
+		t.Errorf("expected escaped script tag in output: %q", html)
+	}
+}
+
 func TestUserTheme(t *testing.T) {
 	dir := t.TempDir()
 	t.Setenv("XDG_CONFIG_HOME", dir)