Implement consistent logging

Example using {logger}:
```
library(logger)

log_appender(appender_stdout)
log_threshold(INFO)

log_info("App started")
log_warn("Potential issue")
log_error("Something failed")
```
Inside Shiny:
```
observeEvent(input$submit, {
  log_info("Submit pressed by user")
})
```
The Shiny logs then give you levels, timestamps, formatting, etc.