making proper api citation

paper/.latexmkrc

@@ -1,6 +1,7 @@
 $pdf_mode = 1;
 $pdflatex = 'pdflatex -synctex=1 -interaction=nonstopmode -file-line-error %O %S';
-$bibtex_use = 2;                       # run bibtex when needed
-$bibtex   = 'bibtex %O %B';
+$bibtex_use = 2;                       # run biber when biblatex .bcf changes
+# biber runs with cwd = -outdir (paper/build); .bib paths are relative to paper/src
+$biber    = 'biber --input-directory=../src %O %S';
 $pdf_previewer = 'zathura %O %S';
 $clean_ext = 'synctex.gz bbl bcf run.xml fls fdb_latexmk glg glo gls ist blg lof lot out toc';

paper/src/preamble.tex

@@ -25,6 +25,7 @@
 \usepackage{graphicx}
 \usepackage{hyperref}
 \usepackage{booktabs}
+\usepackage[american]{babel}
 \usepackage{csquotes}
 \usepackage{subcaption}
 \usepackage{siunitx}
@@ -57,8 +58,8 @@
     literate={·}{{\textperiodcentered}}1 {−}{{\textminus}}1 {—}{{---}}1 {–}{{--}}1
 }
 
-% Use biblatex with authoryear style for in-text citations like (Author, Year)
-\usepackage[backend=bibtex,style=authoryear,natbib=true,maxcitenames=2]{biblatex}
+% APA 7-style references and citations (requires biber)
+\usepackage[style=apa,backend=biber]{biblatex}
 \addbibresource{bib/references.bib}
 
 % Page headers (SciTech format)