chore: add devbox setup and ignore Quartus build files

.gitignore

@@ -0,0 +1,18 @@
+# Quartus build artifacts and workspace state
+fpga/**/db/
+fpga/**/incremental_db/
+fpga/**/output_files/
+fpga/**/simulation/
+*.qws
+*.qsf.bak
+*.qarlog
+*.rpt
+*.summary
+*.smsg
+*.done
+*.jdi
+*.pin
+*.sld
+
+# Devbox
+.devbox/