This PR fixes dashboard installation failures by improving HTTP error handling and adding retry logic for network issues.
## Problem
Users were experiencing dashboard installation failures with cryptic error messages like "error sending request for url" when network issues occurred or when GitHub releases were temporarily unavailable.
## Changes
- **Enhanced HTTP client**: Added proper User-Agent, timeouts (120s total, 30s connect), and better error formatting
- **Retry logic**: Added exponential backoff retry (up to 3 attempts) for connection errors and server errors (5xx)
- **Better error messages**: Improved error formatting with full error chain context
- **Comprehensive tests**: Added unit tests for various failure scenarios (404, connection errors, partial downloads)
## Implementation Details
- Replaced direct `reqwest::get()` calls with a configured HTTP client
- Added `format_reqwest_error()` to provide detailed error context
- Implemented retry logic in `download_bytes()` with exponential backoff
- Added extensive test coverage including mock HTTP server scenarios
Fixes#1146
Chris Tate
44f37c92d3