docs: add XML doc comments across src + Sister Projects section in CLAUDE.md

Bulk CommentChecker pass: fills in <param>/<inheritdoc> tags on public
APIs across all 23 src/ projects so the doc-coverage gate is green. Also
adds a Sister Projects section to CLAUDE.md pointing at the MxAccess
Gateway and OtOpcUa sibling repos, and gitignores local credential
captures (*login*.txt) and the wonder-app-vd03 deploy/ artifacts.

src/ScadaLink.ConfigurationDatabase/Configurations/InboundApiConfiguration.cs

@@ -6,6 +6,8 @@ namespace ScadaLink.ConfigurationDatabase.Configurations;
 
 public class ApiKeyConfiguration : IEntityTypeConfiguration<ApiKey>
 {
+    /// <summary>Configures the EF Core mapping for the <see cref="ApiKey"/> entity.</summary>
+    /// <param name="builder">Entity type builder used to apply the configuration.</param>
     public void Configure(EntityTypeBuilder<ApiKey> builder)
     {
         builder.HasKey(k => k.Id);
@@ -28,6 +30,8 @@ public class ApiKeyConfiguration : IEntityTypeConfiguration<ApiKey>
 
 public class ApiMethodConfiguration : IEntityTypeConfiguration<ApiMethod>
 {
+    /// <summary>Configures the EF Core mapping for the <see cref="ApiMethod"/> entity.</summary>
+    /// <param name="builder">Entity type builder used to apply the configuration.</param>
     public void Configure(EntityTypeBuilder<ApiMethod> builder)
     {
         builder.HasKey(m => m.Id);