docs: add FAPP research paper LaTeX sources

Add paper directory with LaTeX source, bibliography, and Makefile
for the FAPP (Federated Application Protocol) research paper.
Build artifacts are gitignored.

paper/Makefile

@@ -0,0 +1,22 @@
+MAIN = fapp
+BIB  = fapp-refs
+
+.PHONY: all clean watch
+
+all: $(MAIN).pdf
+
+$(MAIN).pdf: $(MAIN).tex $(BIB).bib
+	pdflatex -interaction=nonstopmode $(MAIN)
+	bibtex $(MAIN)
+	pdflatex -interaction=nonstopmode $(MAIN)
+	pdflatex -interaction=nonstopmode $(MAIN)
+
+clean:
+	rm -f $(MAIN).{aux,bbl,blg,log,out,pdf,toc,lof,lot,fls,fdb_latexmk,synctex.gz}
+
+watch:
+	@echo "Watching for changes..."
+	@while true; do \
+		inotifywait -qe modify $(MAIN).tex $(BIB).bib 2>/dev/null || sleep 2; \
+		$(MAKE) all; \
+	done