stacks/news-digest: favicon + serve-via-nginx wiring

Editorial-briefing favicon: 32×32 SVG, Australis palette. Cyan
masthead-rule across the top echoes the page's aurora-rule, four
descending text-line indicators below evoke a newspaper column.
Reads cleanly at 16×16 (the typical browser tab size). Static
markup only — no script, no animation — so all browsers honor
it for tab + bookmark icons.

Linked from both digest.html.j2 and archive.html.j2 with the
proper type="image/svg+xml" attribute. Served by nginx from
the bind-mounted /output dir alongside index.html and style.css.

Deploy playbook also updated to copy the favicon into /output at
deploy-time so a fresh deploy doesn't 404 on the icon before the
first cron fire.

playbooks/deploy-news-digest.yaml

@@ -80,6 +80,12 @@ steps:
       dest: "{{ compose_dir }}/templates/style.css"
       mode: "0644"
 
+  - name: Upload templates/favicon.svg
+    upload:
+      src: stacks/news-digest/templates/favicon.svg
+      dest: "{{ compose_dir }}/templates/favicon.svg"
+      mode: "0644"
+
   - name: Seed .env from template (only if absent)
     upload:
       src: stacks/news-digest/.env.example
@@ -104,12 +110,14 @@ steps:
       cd {{ compose_dir }} && DOCKER_BUILDKIT=0 docker compose build 2>&1 \
         | grep -vE '^Step [0-9]+/[0-9]+ : (RUN|COPY)|^Removing intermediate|^ ---> |^ ---> Running|Collecting|Downloading|Requirement|Using cached|Installing collected|Successfully (installed|built)|━'
 
-  - name: Pre-stage style.css into /output so the first page render works
-    # Worker writes index.html which references "style.css" (relative).
-    # The CSS isn't generated by the worker; nginx serves whichever
-    # copy lands at /usr/share/nginx/html/style.css. Copy the template
-    # CSS into the bind-mounted /output dir at deploy-time.
-    shell: cp -f {{ compose_dir }}/templates/style.css {{ output_dir }}/style.css
+  - name: Pre-stage style.css + favicon.svg into /output for nginx
+    # The worker writes HTML that references "style.css" and
+    # "favicon.svg" (relative). Neither is generated dynamically;
+    # nginx serves whichever copy lands at /usr/share/nginx/html/.
+    # Copy both from the templates dir at deploy-time.
+    shell: |
+      cp -f {{ compose_dir }}/templates/style.css {{ output_dir }}/style.css
+      cp -f {{ compose_dir }}/templates/favicon.svg {{ output_dir }}/favicon.svg
 
   - name: docker compose up -d
     shell: cd {{ compose_dir }} && docker compose up -d