Fix ANOVA and pairwise gene set enrichment and spatial registration plot visualization

[manishabarse]

I noticed some plots failed because the color mappings did not include pairwise spatial domain (SpD) comparisons (e.g., L1-L2) or the overall ANOVA result. ANOVA gene set enrichment also encountered issues with result column names and single-column data frames being simplified to vectors.

Changes

• Add color handling for pairwise SpD comparisons by deriving colors from the corresponding domain colors.
• Use neutral grey for overall ANOVA results, which do not represnt individual SpDs.
• Standardize ANOVA result column names for downstream plotting.
• Preserve data frame structure for single-column ANOVA results using drop = FALSE.
• Add golem:: to app launch function.
• Add scales to DESCRIPTION file used for color interpolation.

Implementation

• Automatically generate midpoint colors for pairwise comparisons from the user-supplied colors of the corresponding SpDs, so users do not need to define colors for every pairwise comparison.
• Use a grey fallback when the colors for the corresponding SpDs are unavailable.
• Handle overall ANOVA result colors separately from the colors used for enrichment and pairwise statistics.
• Normalize ANOVA result column names in the app without modifying the original modeling results.

Validation / Testing

• Tested the updated plotting code locally in RStudio udimg the example from run_app.R script.
• Also tested the working with current DLPFC_ASD data
• Verified that ANOVA gene set enrichment and the spatial registration plots SpD color handling work as expected.
• Checked the plots with @Nick-Eagles and we think ANOVA plots look as would be expected.