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/handlers/auth.go

@@ -137,6 +137,11 @@ func AuthMiddleware() gin.HandlerFunc {
 		}
 
 		authHeader := c.GetHeader("Authorization")
+		if authHeader == "" {
+			if tokenParam := c.Query("token"); tokenParam != "" {
+				authHeader = "Bearer " + tokenParam
+			}
+		}
 		if authHeader == "" {
 			c.JSON(401, gin.H{"error": "Authorization header required"})
 			c.Abort()
@@ -230,6 +235,9 @@ func Register(c *gin.Context) {
 		return
 	}
 
+	// Provision messaging defaults (self chat, password vault, global channels).
+	_ = ensureMessagingDefaults(db, user.ID)
+
 	// Generate JWT token
 	token, err := GenerateJWT(user)
 	if err != nil {