Qualify all {.help} tags with AMR:: and convert backtick ?func references

- Add AMR:: namespace prefix and trailing () to all {.help} cli markup
  so they render as clickable help links (e.g. {.help AMR::as.sir}())
- Convert `?funcname` backtick-quoted help references to {.help AMR::funcname}()
  in aa_helper_functions.R, custom_eucast_rules.R, interpretive_rules.R,
  key_antimicrobials.R, mo.R, plotting.R, resistance_predict.R, and sir.R
- Skipped `?proportion` in sir_calc.R as 'proportion' is not exported

https://claude.ai/code/session_01XHWLohiSTdZvCutwD7ag2b

R/aa_helper_functions.R

@@ -928,7 +928,7 @@ ascertain_sir_classes <- function(x, obj_name) {
     warning_(
       "the data provided in argument `", obj_name,
       "` should contain at least one column of class 'sir'. Eligible SIR column were now guessed. ",
-      "See `?as.sir`.",
+      "See {.help AMR::as.sir}().",
       immediate = TRUE
     )
     sirs_eligible <- is_sir_eligible(x)