fix(demo): repair Kiwix service with catalog-based ZIM bootstrap

Kiwix was failing to start: its inline bootstrap command had a shell
syntax error (a YAML-wrapped multi-line wget left a dangling `||`), and
the hard-coded sample-ZIM URL returned 404 because Kiwix rotates the
date-stamped filenames monthly.

Replace the inline command with a bind-mounted bootstrap script that
resolves the current ZIM filename from the Kiwix OPDS catalog at startup,
so the download URL never rots. kiwix-serve is also started on port 8080
to match the container port mapping and healthcheck (it defaults to 80).

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

demo/config/kiwix/bootstrap.sh

@@ -0,0 +1,45 @@
+#!/bin/sh
+# Kiwix bootstrap: ensure a sample ZIM file is present, then serve it.
+#
+# ZIM filenames on download.kiwix.org are date-stamped and rotate monthly,
+# so hard-coded URLs rot quickly. Instead this script resolves the current
+# filename from the Kiwix OPDS catalog, which always points at the live file.
+
+set -u
+
+ZIM_DIR=/data
+ZIM_FILE=devdocs_en_lit.zim
+CATALOG_URL='https://library.kiwix.org/catalog/v2/entries?name=devdocs_en_lit&count=1'
+MAX_ATTEMPTS=6
+RETRY_DELAY=5
+
+if ! ls "$ZIM_DIR"/*.zim >/dev/null 2>&1; then
+    echo "[kiwix] No ZIM files found; resolving a sample ZIM from the Kiwix catalog..."
+    attempt=0
+    while [ "$attempt" -lt "$MAX_ATTEMPTS" ]; do
+        attempt=$((attempt + 1))
+        zim_url=$(wget -q -O - "$CATALOG_URL" 2>/dev/null \
+                  | grep -o 'https://[^"]*\.zim\.meta4' | head -n1 \
+                  | sed 's/\.meta4$//')
+        if [ -n "$zim_url" ]; then
+            echo "[kiwix] Downloading: $zim_url"
+            if wget -q --timeout=60 -O "$ZIM_DIR/$ZIM_FILE" "$zim_url"; then
+                echo "[kiwix] Download complete."
+                break
+            fi
+            rm -f "$ZIM_DIR/$ZIM_FILE"
+            echo "[kiwix] Download failed; retrying in ${RETRY_DELAY}s..."
+        else
+            echo "[kiwix] Catalog lookup failed; retrying in ${RETRY_DELAY}s..."
+        fi
+        sleep "$RETRY_DELAY"
+    done
+fi
+
+if ls "$ZIM_DIR"/*.zim >/dev/null 2>&1; then
+    echo "[kiwix] Starting kiwix-serve..."
+    exec kiwix-serve --port 8080 "$ZIM_DIR"/*.zim
+else
+    echo "[kiwix] No ZIM files available; sleeping indefinitely."
+    exec sleep infinity
+fi