feat(messages): implement integrated chat with voice/calls and tidy root go module

Add Discord-like messaging APIs, websocket realtime, smart suggestions, password vault flows, semantic indexing integration, and new /app/messages UI.

Add typing indicators, advanced message search filters, voice notes, browser-local optional transcription, and WebRTC call signaling (offer/answer/ice/hangup).

Clean root go.mod via go mod tidy and remove stale root go.sum.

backend/services/message_detector_test.go

@@ -0,0 +1,83 @@
+package services
+
+import "testing"
+
+func TestDetectMessageContent_URLsAndSuggestions(t *testing.T) {
+	body := "Check this out https://github.com/trackeep/backend and video https://youtu.be/dQw4w9WgXcQ"
+
+	suggestions, attachments, isSensitive := DetectMessageContent(body)
+	if isSensitive {
+		t.Fatalf("expected non-sensitive message")
+	}
+
+	if len(attachments) < 2 {
+		t.Fatalf("expected at least 2 attachments, got %d", len(attachments))
+	}
+
+	hasGitHub := false
+	hasYouTube := false
+	for _, s := range suggestions {
+		if s.Type == "link_github" {
+			hasGitHub = true
+		}
+		if s.Type == "save_youtube" {
+			hasYouTube = true
+		}
+	}
+
+	if !hasGitHub {
+		t.Fatalf("expected link_github suggestion")
+	}
+	if !hasYouTube {
+		t.Fatalf("expected save_youtube suggestion")
+	}
+}
+
+func TestDetectMessageContent_TaskAndEventIntents(t *testing.T) {
+	body := "TODO: schedule meeting tomorrow at 10am to review the release plan"
+	suggestions, _, _ := DetectMessageContent(body)
+
+	hasTask := false
+	hasEvent := false
+	for _, s := range suggestions {
+		if s.Type == "create_task" {
+			hasTask = true
+		}
+		if s.Type == "create_event" {
+			hasEvent = true
+		}
+	}
+
+	if !hasTask {
+		t.Fatalf("expected create_task suggestion")
+	}
+	if !hasEvent {
+		t.Fatalf("expected create_event suggestion")
+	}
+}
+
+func TestDetectMessageContent_PasswordWarning(t *testing.T) {
+	body := "password: SuperSecret123!"
+	suggestions, _, isSensitive := DetectMessageContent(body)
+	if !isSensitive {
+		t.Fatalf("expected sensitive message")
+	}
+
+	hasWarning := false
+	hasVaultMove := false
+	for _, s := range suggestions {
+		if s.Type == "password_warning" {
+			hasWarning = true
+		}
+		if s.Type == "move_to_password_vault" {
+			hasVaultMove = true
+		}
+	}
+
+	if !hasWarning {
+		t.Fatalf("expected password_warning suggestion")
+	}
+	if !hasVaultMove {
+		t.Fatalf("expected move_to_password_vault suggestion")
+	}
+}