fix(plugins): add base64 handling for []byte and remove raw=true (#5121)

* fix(plugins): add base64 handling for []byte and remove raw=true

Go's json.Marshal automatically base64-encodes []byte fields, but Rust's
serde_json serializes Vec<u8> as a JSON array and Python's json.dumps
raises TypeError on bytes. This fixes both directions of plugin
communication by adding proper base64 encoding/decoding in generated
client code.

For Rust templates (client and capability): adds a base64_bytes serde
helper module with #[serde(with = "base64_bytes")] on all Vec<u8> fields,
and adds base64 as a dependency. For Python templates: wraps bytes params
with base64.b64encode() and responses with base64.b64decode().

Also removes the raw=true binary framing protocol from all templates,
the parser, and the Method type. The raw mechanism added complexity that
is no longer needed once []byte works properly over JSON.

* fix(plugins): update production code and tests for base64 migration

Remove raw=true annotation from SubsonicAPI.CallRaw, delete all raw
test fixtures, remove raw-related test cases from parser, generator, and
integration tests, and add new test cases validating base64 handling
for Rust and Python templates.

* fix(plugins): update golden files and regenerate production code

Update golden test fixtures for codec and comprehensive services to
include base64 handling for []byte fields. Regenerate all production
PDK code (Go, Rust, Python) and host wrappers to use standard JSON
with base64-encoded byte fields instead of binary framing protocol.

* refactor: remove base64 helper duplication from rust template

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(plugins): add base64 dependency to capabilities' Cargo.toml

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

plugins/cmd/ndpgen/internal/templates/capability.rs.tmpl

@@ -7,6 +7,7 @@ use serde::{Deserialize, Serialize};
 {{- if hasHashMap .Capability}}
 use std::collections::HashMap;
 {{- end}}
+{{- if .Capability.HasByteFields}}{{template "base64_bytes_module" .}}{{- end}}
 
 // Helper functions for skip_serializing_if with numeric types
 #[allow(dead_code)]
@@ -70,6 +71,9 @@ pub struct {{.Name}} {
     #[serde(default, skip_serializing_if = "{{skipSerializingFunc .Type}}")]
 {{- else}}
     #[serde(default)]
+{{- end}}
+{{- if .IsByteSlice}}
+    #[serde(with = "base64_bytes")]
 {{- end}}
     pub {{rustFieldName .Name}}: {{fieldRustType .}},
 {{- end}}