Do not import bus/taxy/ferry-only platforms (#589)

Fixes #575

Always import `railway = platform`.

For `public_transport = platform`:
- Always import if `train = yes`
- Always import if `tram = yes`
- Always import if `subway = yes`
- Always import if `light_rail = yes`
- Else, do not import if any of `bus = yes` or `trolleybus = yes` or
`share_taxi = yes` or `ferry = yes`.



Also see
https://taginfo.openstreetmap.org/tags/public_transport=platform#combinations

(https://openrailwaymap.app/#view=18.46/52.5287048/13.3768069)
Before:
<img width="1099" height="829" alt="image"
src="https://github.com/user-attachments/assets/ea1c003d-e516-49c6-a12d-2bff5bf5b0a1"
/>

After:
<img width="1281" height="759" alt="image"
src="https://github.com/user-attachments/assets/495a08ce-15e4-4a6c-85dd-d03391061784"
/>

Author: hiddewie

import/openrailwaymap.lua

@@ -825,6 +825,26 @@ function format_railway_position(item)
   end
 end
 
+function is_railway_platform(tags)
+  -- Ignore non-railway platforms
+  return tags.railway == 'platform'
+    or (
+      tags.public_transport == 'platform'
+      and (
+        tags.train == 'yes'
+        or tags.tram == 'yes'
+        or tags.subway == 'yes'
+        or tags.light_rail == 'yes'
+        or not (
+          tags.bus == 'yes'
+          or tags.trolleybus == 'yes'
+          or tags.share_taxi == 'yes'
+          or tags.ferry == 'yes'
+        )
+      )
+    )
+end
+
 local railway_station_values = osm2pgsql.make_check_values_func({'station', 'halt', 'tram_stop', 'service_station', 'yard', 'junction', 'spur_junction', 'crossover', 'site'})
 local railway_poi_values = osm2pgsql.make_check_values_func(tag_functions.poi_railway_values)
 local railway_signal_values = osm2pgsql.make_check_values_func({'signal', 'buffer_stop', 'derail', 'vacancy_detection'})
@@ -924,7 +944,7 @@ function osm2pgsql.process_node(object)
     })
   end
 
-  if tags.public_transport == 'platform' or tags.railway == 'platform' then
+  if is_railway_platform(tags) then
     platforms:insert({
       way = object:as_point(),
       name = tags.name,
@@ -1165,7 +1185,7 @@ function osm2pgsql.process_way(object)
     end
   end
 
-  if tags.public_transport == 'platform' or tags.railway == 'platform' then
+  if is_railway_platform(tags) then
     platforms:insert({
       way = object:as_polygon(),
       name = tags.name,
@@ -1268,7 +1288,7 @@ local route_platform_relation_roles = osm2pgsql.make_check_values_func({'platfor
 function osm2pgsql.process_relation(object)
   local tags = object.tags
 
-  if tags.public_transport == 'platform' or tags.railway == 'platform' then
+  if is_railway_platform(tags) then
     platforms:insert({
       way = object:as_multipolygon(),
       name = tags.name,