chore: raise minimum requirements to match supported versions

Now that 5.1-stable is dropped from CI, align the documented/enforced minimums:

- init.rb: requires_redmine 5.1.0 -> 6.0.0
- README: Redmine >= 6.0.0, add Ruby >= 3.3, PostgreSQL >= 13 -> 15,
  PostGIS >= 3.0 -> 3.4, NodeJS v18 -> >= 22
- CI: install Node 22 (setup_20.x -> setup_22.x) to match the README minimum
  (Node 20 nears EOL; 22 is current LTS)

Author: dkastl

.github/workflows/test-postgis.yml

@@ -86,7 +86,7 @@ jobs:
 
       - name: Install Node/Yarn packages
         run: |
-          curl -sL https://deb.nodesource.com/setup_20.x | bash -
+          curl -sL https://deb.nodesource.com/setup_22.x | bash -
           curl -sL https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add -
           echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list
           apt-get update --yes --quiet

README.md

@@ -17,10 +17,11 @@ The Geo-Task-Tracker (GTT) plugin adds spatial capabilities to Redmine:
 Redmine GTT plugins **require PostgreSQL/PostGIS** and will not work with SQLite
 or MariaDB/MySQL!!!
 
-- Redmine >= 5.1.0
-- PostgreSQL >= 13
-- PostGIS >= 3.0
-- NodeJS v18
+- Redmine >= 6.0.0
+- Ruby >= 3.3
+- PostgreSQL >= 15
+- PostGIS >= 3.4
+- NodeJS >= 22
 - yarn
 
 ## Installation

init.rb

@@ -8,7 +8,7 @@
   description 'Adds location-based task management and maps'
   version '6.0.1'
 
-  requires_redmine :version_or_higher => '5.1.0'
+  requires_redmine :version_or_higher => '6.0.0'
 
   project_module :gtt do
     permission :manage_gtt_settings, {