feat(templates): add hap_backend_longlived override template

Generic long-lived backend (template_override='hap_backend_longlived') for apps
whose primary path holds connections open: streaming, large up/downloads,
persistent sessions. Both primary and SSE backends tuned long-lived (no
http-server-close, http-no-delay, 6h server/tunnel/keep-alive). Differs from
hap_backend_websocket (which only long-lives the SSE variant).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

templates/hap_backend_longlived.tpl

@@ -0,0 +1,41 @@
+# Long-lived backend for {{ name }} (template_override='hap_backend_longlived').
+# Use for apps whose PRIMARY traffic holds connections open: media streaming,
+# large up/downloads, or persistent viewer/streaming sessions. Both the primary
+# and the SSE backend are tuned long-lived here (no http-server-close,
+# http-no-delay, 6h server/tunnel/keep-alive timeouts).
+#
+# Compare hap_backend_websocket.tpl, which keeps the PRIMARY backend standard
+# and only makes the -sse-backend long-lived. Pick this one when the main path
+# itself needs long-lived connections, not just an SSE side-channel.
+backend {{ name }}-backend
+    no option http-server-close
+    option http-no-delay
+    timeout server 6h
+    timeout tunnel 6h
+    timeout http-keep-alive 6h
+    option forwardfor
+    http-request add-header X-CLIENT-IP %[var(txn.real_ip)]
+    http-request set-header X-Real-IP %[var(txn.real_ip)]
+    http-request set-header X-Forwarded-For %[var(txn.real_ip)]
+    http-request set-header X-Forwarded-Proto https if { ssl_fc }
+    http-request set-header X-Forwarded-Proto http if !{ ssl_fc }
+    {% for server in servers %}
+    server {{ server.server_name }} {{ server.server_address }}:{{ server.server_port }} {{ server.server_options }} resolvers docker_dns init-addr last,libc,none
+    {% endfor %}
+
+# SSE variant (Accept: text/event-stream / ?action=stream auto-routes here)
+backend {{ name }}-sse-backend
+    no option http-server-close
+    option http-no-delay
+    timeout server 6h
+    timeout tunnel 6h
+    timeout http-keep-alive 6h
+    option forwardfor
+    http-request add-header X-CLIENT-IP %[var(txn.real_ip)]
+    http-request set-header X-Real-IP %[var(txn.real_ip)]
+    http-request set-header X-Forwarded-For %[var(txn.real_ip)]
+    http-request set-header X-Forwarded-Proto https if { ssl_fc }
+    http-request set-header X-Forwarded-Proto http if !{ ssl_fc }
+    {% for server in servers %}
+    server {{ server.server_name }} {{ server.server_address }}:{{ server.server_port }} {{ server.server_options }} resolvers docker_dns init-addr last,libc,none
+    {% endfor %}