Migrate to base R pipe (|>) and drop magrittr from Imports

[eboyer221]

Follow-up to #25 per @AbhirupaGhosh's suggestion to use the base R pipe.

Changes

• Replaced all %>% with |> across R/app.R and R/utils.R.
• Removed magrittr from DESCRIPTION Imports (it was only there to enable %>%).
• Removed @importFrom magrittr %>% from R/app.R.
• Regenerated NAMESPACE via devtools::document(), which drops the now-unused importFrom(magrittr,"%>%") line.

Why

• One fewer dependency for users and Bioconductor CI to install, consistent with Bioconductor's dependency-minimization guidance.
• |> has been the standard R forward pipe since R 4.1 (2021); DESCRIPTION already requires R >= 4.5.0, so no version compatibility concern.

Test plan

1. devtools::load_all() then launchAMRDashboard() — dashboard builds and tabs render normally.
2. grep -rn "%>%" R/ returns no hits.
3. grep -n "magrittr" DESCRIPTION NAMESPACE R/ returns no hits.

[amcim]

The changes were made, everything ran, and the primary concern of this switch (which is using a "." placeholder) is dealt with, so approved for merge