Print Host: add Moonraker (Klipper) host type (#13991)

OrcaSlicer currently ships an "Octo/Klipper" host type that maps to the
OctoPrint REST endpoints (api/version, api/files/local). It works for
Klipper setups that run Moonraker with the OctoPrint-emulation plugin,
but native Moonraker — and Moonraker-compatible firmwares like the
Prusa-Firmware-Buddy buddy-klipper fork — speak a different shape:
distinct paths, JSON body for /printer/print/start, {"result":...}
envelope. There's no host type for that today.

Add a new Moonraker class deriving from PrintHost. Endpoints used,
matching the Moonraker spec:

- GET  /server/info                      — connection test, reads
                                            result.klippy_state
- GET  /server/files/roots               — storage-picker dropdown
                                            (returns roots with 'w'
                                            permission); gracefully
                                            degrades if absent
- POST /server/files/upload (multipart)  — upload (form fields:
                                            file, root)
- POST /printer/print/start (json)       — {"filename":"<path>"}; the
                                            filename is whatever the
                                            upload response returned
                                            in result.item.path, so any
                                            server-side rename
                                            (collision suffix etc.) is
                                            respected. JSON body is
                                            built via property_tree
                                            write_json so exotic
                                            characters in the path are
                                            properly escaped.

Auth: X-Api-Key header, only when printhost_apikey is non-empty
(Moonraker can be configured to require it but doesn't by default).
HTTP Basic / Digest are not part of the Moonraker spec and are not
sent.

Storage root is read from upload_data.storage with "gcodes" as the
fallback default, so the existing storage-picker plumbing in
PrintHostDialogs lights up automatically once enumerable roots are
returned.

UI: registers as the "Moonraker (Klipper)" entry under host_type;
selectable via the existing Physical Printer dialog (sidebar's
connection button on the printer card).

Verified against a Prusa-Firmware-Buddy buddy-klipper fork (firmware
identifies as moonraker_version "0.8.0-prusalink-shim"): /server/info
test, multipart upload to /server/files/upload, and JSON
/printer/print/start all work end-to-end. The existing "Octo/Klipper"
entry is left untouched so users currently relying on Moonraker's
OctoPrint-emulation plugin keep working.

src/libslic3r/PrintConfig.cpp

@@ -149,7 +149,8 @@ static t_config_enum_values s_keys_map_PrintHostType {
     { "flashforge",     htFlashforge },
     { "simplyprint",    htSimplyPrint },
     { "elegoolink",     htElegooLink },
-    { "3dprinteros",    ht3DPrinterOS }
+    { "3dprinteros",    ht3DPrinterOS },
+    { "moonraker",      htMoonraker }
 };
 CONFIG_OPTION_ENUM_DEFINE_STATIC_MAPS(PrintHostType)
 
@@ -4862,6 +4863,7 @@ void PrintConfigDef::init_fff_params()
     def->enum_values.push_back("simplyprint");
     def->enum_values.push_back("elegoolink");
     def->enum_values.push_back("3dprinteros");
+    def->enum_values.push_back("moonraker");
     def->enum_labels.push_back("PrusaLink");
     def->enum_labels.push_back("PrusaConnect");
     def->enum_labels.push_back("Octo/Klipper");
@@ -4877,6 +4879,7 @@ void PrintConfigDef::init_fff_params()
     def->enum_labels.push_back("SimplyPrint");
     def->enum_labels.push_back("Elegoo Link");
     def->enum_labels.push_back("3DPrinterOS");
+    def->enum_labels.push_back("Moonraker (Klipper)");
     def->mode = comAdvanced;
     def->cli = ConfigOptionDef::nocli;
     def->set_default_value(new ConfigOptionEnum<PrintHostType>(htOctoPrint));