Port Brave Sync server to Rust

Use SQLite for persistence and generate Rust protobuf bindings at build time.

Add Docker image support for containerized deployment.

Co-Authored-By: codex <[email protected]>

schema/protobuf/sync_pb/encryption.proto

@@ -0,0 +1,36 @@
+// Copyright 2012 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Common sync protocol for encrypted data.
+
+// If you change or add any fields in this file, update proto_visitors.h and
+// potentially proto_enum_conversions.{h, cc}.
+
+syntax = "proto2";
+
+option go_package = "./sync_pb";
+
+option java_multiple_files = true;
+option java_package = "org.chromium.components.sync.protocol";
+
+option optimize_for = LITE_RUNTIME;
+
+package sync_pb;
+
+// Encrypted sync data consists of two parts: a key name and a blob. Key name is
+// the name of the key that was used to encrypt blob and blob is encrypted data
+// itself.
+//
+// The reason we need to keep track of the key name is that a sync user can
+// change their passphrase (and thus their encryption key) at any time. When
+// that happens, we make a best effort to reencrypt all nodes with the new
+// passphrase, but since we don't have transactions on the server-side, we
+// cannot guarantee that every node will be reencrypted. As a workaround, we
+// keep track of all keys, assign each key a name (by using that key to encrypt
+// a well known string) and keep track of which key was used to encrypt each
+// node.
+message EncryptedData {
+  optional string key_name = 1;
+  optional string blob = 2;  // base64-encoded.
+}