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/testdata/codec_client_expected.py

@@ -12,6 +12,7 @@ from typing import Any
 
 import extism
 import json
+import base64
 
 
 class HostFunctionError(Exception):
@@ -38,7 +39,7 @@ def codec_encode(data: bytes) -> bytes:
         HostFunctionError: If the host function returns an error.
     """
     request = {
-        "data": data,
+        "data": base64.b64encode(data).decode("ascii"),
     }
     request_bytes = json.dumps(request).encode("utf-8")
     request_mem = extism.memory.alloc(request_bytes)
@@ -49,4 +50,4 @@ def codec_encode(data: bytes) -> bytes:
     if response.get("error"):
         raise HostFunctionError(response["error"])
 
-    return response.get("result", b"")
+    return base64.b64decode(response.get("result", ""))