Enhance Windows dev support (#13)

Makes local dev work on Windows: cross-env for the server dev port, pnpm --parallel to run server+web together (replacing the POSIX-only '&'), PowerShell setup docs, engines widened to Node >=20, and a Node 20 + 24 CI matrix.

CI keeps a stable required 'Build & test' status via an aggregate gate job so the matrix rename doesn't drop the context the main ruleset requires.

Co-authored-by: BadAtCaptchas <2359196+BadAtCaptchas@users.noreply.github.com>
Co-authored-by: Jannis Braun <151788261+TheZwiss@users.noreply.github.com>

pnpm-lock.yaml

@@ -120,6 +120,9 @@ importers:
       '@types/ws':
         specifier: ^8.18.1
         version: 8.18.1
+      cross-env:
+        specifier: ^7.0.3
+        version: 7.0.3
       drizzle-kit:
         specifier: ^0.24.0
         version: 0.24.2
@@ -2656,6 +2659,11 @@ packages:
   crc@3.8.0:
     resolution: {integrity: sha512-iX3mfgcTMIq3ZKLIsVFAbv7+Mc10kxabAGQb8HvjA1o3T1PIYprbakQ65d3I+2HGHt6nSKkM9PYjgoJO2KcFBQ==}
 
+  cross-env@7.0.3:
+    resolution: {integrity: sha512-+/HKd6EgcQCJGh2PSjZuUitQBQynKor4wrFbRg4DtAgS1aWO+gU52xpH7M9ScGgXSYmAVS9bIJ8EzuaGw0oNAw==}
+    engines: {node: '>=10.14', npm: '>=6', yarn: '>=1'}
+    hasBin: true
+
   cross-spawn@7.0.6:
     resolution: {integrity: sha512-uV2QOWP2nWzsy2aMp8aRibhi9dlzF5Hgh5SHaB9OiTGEyDTiJJyx0uy51QXdyWbtAHNua4XJzUKca3OzKUd3vA==}
     engines: {node: '>= 8'}
@@ -7993,6 +8001,10 @@ snapshots:
       buffer: 5.7.1
     optional: true
 
+  cross-env@7.0.3:
+    dependencies:
+      cross-spawn: 7.0.6
+
   cross-spawn@7.0.6:
     dependencies:
       path-key: 3.1.1