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/parser.go

@@ -761,7 +761,6 @@ func parseMethod(name string, funcType *ast.FuncType, annotation map[string]stri
 	m := Method{
 		Name:       name,
 		ExportName: annotation["name"],
-		Raw:        annotation["raw"] == "true",
 		Doc:        doc,
 	}
 
@@ -800,13 +799,6 @@ func parseMethod(name string, funcType *ast.FuncType, annotation map[string]stri
 		}
 	}
 
-	// Validate raw=true methods: must return exactly (string, []byte, error)
-	if m.Raw {
-		if !m.HasError || len(m.Returns) != 2 || m.Returns[0].Type != "string" || m.Returns[1].Type != "[]byte" {
-			return m, fmt.Errorf("raw=true method %s must return (string, []byte, error) — content-type, data, error", name)
-		}
-	}
-
 	return m, nil
 }