Mark safe commands with flag_untrusted_safe for whitelist enforcement

Annotate all commands that web UIs (ruTorrent) need for normal torrent
management with _U macro variants, which set flag_untrusted_safe.
Commands not marked are blocked by default for untrusted connections.

Safe commands include:
- d.* download getters, state, priorities, custom fields, start/stop
- f.* file getters, priority control
- p.* peer getters, disconnect, ban/snub
- t.* tracker getters, enable/disable
- throttle.* rate getters/setters, peer limits
- network.* read-only queries (getters safe, setters blocked)
- view.list, view.size, view.filter_all, ui.current_view
- load.*, download_list, d.multicall2, d.multicall.filtered
- convert.*, branch/if/and/or/not/cat/value/print
- system.* version/time/status queries (read-only)
- choke_group.* read-only queries
- method.has_key, method.const, method.list_keys, method.get, strings.*
- group.*.view, group.*.ratio.min/max/upload (dynamic, via flag propagation)

Blocked by default (not marked):
- execute*, method.insert/set/redirect, schedule*, import
- log.*, file.append, network.scgi.open_*, view.filter/sort/event_*
- system.shutdown, system.env, group.insert, choke_group.insert
- All user-defined commands (via method.insert)

src/command_helpers.h

@@ -206,6 +206,10 @@ void initialize_commands();
   CMD2_ANY(key, std::bind(&rpc::command_function_call_object, torrent::Object(torrent::raw_string::from_c_str(cmds)), \
                                std::placeholders::_1, std::placeholders::_2));
 
+#define CMD2_FUNC_SINGLE_U(key, cmds)                                   \
+  CMD2_ANY_U(key, std::bind(&rpc::command_function_call_object, torrent::Object(torrent::raw_string::from_c_str(cmds)), \
+                               std::placeholders::_1, std::placeholders::_2));
+
 #define CMD2_REDIRECT(from_key, to_key)                                 \
   rpc::commands.create_redirect(from_key, to_key, rpc::CommandMap::flag_public_rpc | rpc::CommandMap::flag_dont_delete);
 #define CMD2_REDIRECT_NO_EXPORT(from_key, to_key)                       \