feat: add e2e tests, perf benchmarks, and infrastructure improvements

- messages/bench_test.go: serialization benchmarks (msgpack map vs struct vs protobuf)
- clients/clients_test.go: HTTP client tests with pooling verification (20 tests)
- natsutil/natsutil_test.go: encode/decode roundtrip + binary data tests
- handler/handler_test.go: handler dispatch tests + benchmark
- config/config.go: live reload via fsnotify + RWMutex getter methods
- clients/clients.go: SharedTransport + sync.Pool buffer pooling
- messages/messages.go: typed structs with msgpack+json tags
- messages/proto/: protobuf schema + generated code

Benchmark baseline (ChatRequest roundtrip):
  MsgpackMap:    2949 ns/op, 36 allocs
  MsgpackStruct: 2030 ns/op, 13 allocs (31% faster, 64% fewer allocs)
  Protobuf:       793 ns/op,  8 allocs (73% faster, 78% fewer allocs)

messages/proto/messages.proto

@@ -0,0 +1,174 @@
+syntax = "proto3";
+
+package messages;
+
+option go_package = "git.daviestechlabs.io/daviestechlabs/handler-base/messages/proto";
+
+// ── Pipeline Bridge ─────────────────────────────────────────────────────────
+
+message PipelineTrigger {
+  string request_id = 1;
+  string pipeline   = 2;
+  map<string, string> parameters = 3;
+}
+
+message PipelineStatus {
+  string request_id  = 1;
+  string status      = 2;
+  string run_id      = 3;
+  string engine      = 4;
+  string pipeline    = 5;
+  string submitted_at = 6;
+  string error        = 7;
+  repeated string available_pipelines = 8;
+}
+
+// ── Chat Handler ────────────────────────────────────────────────────────────
+
+message ChatRequest {
+  string request_id       = 1;
+  string user_id          = 2;
+  string message          = 3;
+  string query            = 4;
+  bool   premium          = 5;
+  bool   enable_rag       = 6;
+  bool   enable_reranker  = 7;
+  bool   enable_streaming = 8;
+  int32  top_k            = 9;
+  string collection       = 10;
+  bool   enable_tts       = 11;
+  string system_prompt    = 12;
+  string response_subject = 13;
+}
+
+message ChatResponse {
+  string user_id       = 1;
+  string response      = 2;
+  string response_text = 3;
+  bool   used_rag      = 4;
+  repeated string rag_sources = 5;
+  bool   success       = 6;
+  bytes  audio         = 7;
+  string error         = 8;
+}
+
+message ChatStreamChunk {
+  string request_id = 1;
+  string type       = 2;
+  string content    = 3;
+  bool   done       = 4;
+  int64  timestamp  = 5;
+}
+
+// ── Voice Assistant ─────────────────────────────────────────────────────────
+
+message VoiceRequest {
+  string request_id = 1;
+  bytes  audio      = 2;
+  string language   = 3;
+  string collection = 4;
+}
+
+message VoiceResponse {
+  string request_id    = 1;
+  string response      = 2;
+  bytes  audio         = 3;
+  string transcription = 4;
+  repeated DocumentSource sources = 5;
+  string error         = 6;
+}
+
+message DocumentSource {
+  string text  = 1;
+  double score = 2;
+}
+
+// ── TTS Module ──────────────────────────────────────────────────────────────
+
+message TTSRequest {
+  string text            = 1;
+  string speaker         = 2;
+  string language        = 3;
+  string speaker_wav_b64 = 4;
+  bool   stream          = 5;
+}
+
+message TTSAudioChunk {
+  string session_id   = 1;
+  int32  chunk_index  = 2;
+  int32  total_chunks = 3;
+  bytes  audio        = 4;
+  bool   is_last      = 5;
+  int64  timestamp    = 6;
+  int32  sample_rate  = 7;
+}
+
+message TTSFullResponse {
+  string session_id  = 1;
+  bytes  audio       = 2;
+  int64  timestamp   = 3;
+  int32  sample_rate = 4;
+}
+
+message TTSStatus {
+  string session_id = 1;
+  string status     = 2;
+  string message    = 3;
+  int64  timestamp  = 4;
+}
+
+message TTSVoiceInfo {
+  string name       = 1;
+  string language   = 2;
+  string model_type = 3;
+  string created_at = 4;
+}
+
+message TTSVoiceListResponse {
+  string default_speaker          = 1;
+  repeated TTSVoiceInfo custom_voices = 2;
+  int64  last_refresh             = 3;
+  int64  timestamp                = 4;
+}
+
+message TTSVoiceRefreshResponse {
+  int32  count                        = 1;
+  repeated TTSVoiceInfo custom_voices = 2;
+  int64  timestamp                    = 3;
+}
+
+// ── STT Module ──────────────────────────────────────────────────────────────
+
+message STTStreamMessage {
+  string type       = 1;
+  bytes  audio      = 2;
+  string state      = 3;
+  string speaker_id = 4;
+}
+
+message STTTranscription {
+  string session_id         = 1;
+  string transcript         = 2;
+  int32  sequence           = 3;
+  bool   is_partial         = 4;
+  bool   is_final           = 5;
+  int64  timestamp          = 6;
+  string speaker_id         = 7;
+  bool   has_voice_activity = 8;
+  string state              = 9;
+}
+
+message STTInterrupt {
+  string session_id = 1;
+  string type       = 2;
+  int64  timestamp  = 3;
+  string speaker_id = 4;
+}
+
+// ── Common ──────────────────────────────────────────────────────────────────
+
+message ErrorResponse {
+  bool   error   = 1;
+  string message = 2;
+  string type    = 3;
+}