Add web, state, and backup sections to config template

- [web]: port and public fqdn for the daemon (Caddy proxies from a
  separate jail); port defaults to 8080
- [state]: daemon pidfile and logs directory, default ~/.config/rpn
- [backup]: timestamped dumps for rpnc db backup, default
  ~/.config/rpn/backups; rpnc db restore looks here by default
- cli.md: document the optional positional path and the directory
  defaults for db backup/restore

Application/config.template.toml

@@ -1,6 +1,35 @@
+# RustyRPN configuration template.
+#
+# Copy this file to a real config (config.toml for production,
+# config.dev.toml / config.test.toml for dev and test) and fill in the
+# values. Real config files are gitignored; never commit them.
+#
+# Lookup order: --config <path> flag, then $RUSTYRPN_CONFIG, then
+# config.toml. --env=dev|test selects config.dev.toml / config.test.toml
+# instead of the production config.
+#
+# An empty string means "use the built-in default" where one exists.
+
 [database]
 host = ""
 port = ""
 user = ""
 password = ""
 name = ""
+
+[web]
+# The web server started by `rpnc daemon start`; Caddy reverse-proxies
+# it from a separate jail.
+port = ""       # default 8080
+fqdn = ""       # public hostname, reported by `rpnc daemon status`
+
+[state]
+# Daemon pidfile and logs.
+# Default: ~/.config/rpn
+dir = ""
+
+[backup]
+# Where `rpnc db backup` writes timestamped dumps, and where `rpnc db
+# restore` looks by default.
+# Default: ~/.config/rpn/backups
+dir = ""