chore: stop tracking vendor lib files (now restored via npm + esbuild)

Drops 1038 files from src/Yavsc.Org/wwwroot/lib/ — they remain
on disk and are now restored via 'npm install' at build time
(see package.json and esbuild.config.mjs).

Exception: jonthornton-Datepair is not on npm, the bundled
files are kept in wwwroot/lib/jonthornton-Datepair/ as static
assets.

Also extends .gitignore to ignore:
- node_modules/, build/, package-lock.json (esbuild toolchain)
- wwwroot/js/*.min.js (regenerated by 'npm run build:js')
- .Production.env (added explicitly, not matched by '.*.env'
  glob in some git versions)

This aligns themeok with the architecture already in place
on refac/js-bundle (commits ed7522c5, 196f4b0b, 292c0a2f on
that branch). The build artifacts were already present in
node_modules/ and build/ on disk; this commit only stops
tracking them.

Tested: dotnet test 11/11 green (no C# code touched).

.gitignore

@@ -6,12 +6,28 @@ src/*/obj/
 test/*/bin/
 test/*/obj/
 
+# Toolchain front (Node / esbuild)
+node_modules/
+build/
+package-lock.json
+
+# Libs tierces servies par ASP.NET — restaurées via npm + esbuild.
+# Exception : jonthornton-Datepair n'est pas sur npm, on garde le
+# fichier bundlé comme asset statique.
+src/Yavsc.Org/wwwroot/lib/
+!src/Yavsc.Org/wwwroot/lib/jonthornton-Datepair/
+!src/Yavsc.Org/wwwroot/lib/jonthornton-Datepair/jquery.datepair.min.js
+# Versions .min des libs tierces dans wwwroot/js (elles ne sont plus
+# versionnées ; la minification est faite par esbuild au build)
+src/Yavsc.Org/wwwroot/js/*.min.js
+
 # Exclure les caches lourds
 **/.playwright/
 .git/
 .vs/
 
 .env
+.Production.env
 .*.env
 
 *.csproj.lscache
@@ -20,4 +36,3 @@ appsettings.Development.json
 
 contrib/generated/
 *.tmp
-