Auto-submit IndexNow on deploy when the URL set changes (#130)

Hook the production deploy (deploy/deploy.sh) to ping IndexNow after the health
check passes, so new/changed pages reach Bing/DuckDuckGo/Yandex without a manual
run. Best-effort — wrapped so it can never fail a deploy — and it sources
/etc/thermograph.env so its key matches the one the running service serves.

To avoid re-blasting ~14k URLs on every code push, indexnow.py gains a
--if-changed mode gated by a signature of the URL set (persisted to
data/indexnow_state.txt): code-only deploys skip; a deploy that adds or removes a
city submits. `make indexnow` still forces a full submit.

deploy/deploy.sh

@@ -20,6 +20,18 @@ warm_city_archives() {
     </dev/null >"$APP_DIR/logs/warm-cities.log" 2>&1 &
 }
 
+# Notify IndexNow (Bing / DuckDuckGo / Yandex) of the site's URLs, but only when
+# the set of pages actually changed (a new/removed city) — code-only deploys skip,
+# so we don't re-blast ~14k URLs every push. Best-effort: never fails the deploy.
+# Sourcing the env matches the key the running service serves at /{key}.txt.
+ping_indexnow() {
+  echo "==> Pinging IndexNow (only if the URL set changed)"
+  ( set -a; . /etc/thermograph.env 2>/dev/null || true; set +a
+    base="${THERMOGRAPH_BASE_URL:-https://thermograph.org}"
+    cd "$APP_DIR/backend" && "$APP_DIR/.venv/bin/python" indexnow.py --if-changed "$base"
+  ) || echo "!! IndexNow ping failed (non-fatal)" >&2
+}
+
 echo "==> Fetching $BRANCH"
 git fetch --prune origin "$BRANCH"
 git reset --hard "origin/$BRANCH"
@@ -43,6 +55,7 @@ for i in $(seq 1 15); do
   if curl -fsS -o /dev/null "$url"; then
     echo "==> OK: $url is serving"
     warm_city_archives
+    ping_indexnow
     exit 0
   fi
   sleep 1

deploy/thermograph.env.example

@@ -23,5 +23,7 @@ THERMOGRAPH_BASE=/
 # IndexNow key (Bing/DuckDuckGo/Yandex instant re-crawl). Auto-generated to
 # data/indexnow_key.txt on first use; set here to pin a specific key.
 #THERMOGRAPH_INDEXNOW_KEY=
-# Public site URL the IndexNow CLI submits (`make indexnow`).
+# Public site URL for IndexNow. The deploy hook auto-pings IndexNow after a
+# successful deploy, but only when the URL set changed (a new/removed city), so
+# code-only deploys don't resubmit. `make indexnow` forces a full submit.
 THERMOGRAPH_BASE_URL=https://thermograph.org