feat: Add constants and registry infrastructure

Phase 2 & 3 improvements from code review:

Constants/:
- MSBuildVersions.cs - VS version constants
- Conditions.cs - Reusable condition expressions with fluent helpers

Registry/:
- UsingTasksRegistry.cs - Data-driven task registration (16 lines → 5)

Updates:
- SharedPropertyGroups now uses MSBuildVersions constants
- Ready for BuildTransitiveTargetsFactory to adopt these patterns

Benefits:
- Self-documenting version numbers
- Reusable conditions (30+ duplications → helpers)
- Data-driven task registration
- Easier to maintain and extend

Author: JerrettDavis

src/JD.Efcpt.Build.Definitions/Constants/Conditions.cs

@@ -0,0 +1,84 @@
+namespace JD.Efcpt.Build.Definitions.Constants;
+
+/// <summary>
+/// Common MSBuild condition expressions used throughout the build definitions.
+/// Provides type-safe, reusable condition strings to eliminate duplication.
+/// </summary>
+public static class Conditions
+{
+    /// <summary>
+    /// Checks if EFCPT is enabled for the project.
+    /// </summary>
+    public const string EfcptEnabled = "'$(EfcptEnabled)' == 'true'";
+    
+    /// <summary>
+    /// Checks if the current project is a SQL database project.
+    /// </summary>
+    public const string IsSqlProject = "'$(_EfcptIsSqlProject)' == 'true'";
+    
+    /// <summary>
+    /// Checks if the current project is NOT a SQL database project.
+    /// </summary>
+    public const string IsNotSqlProject = "'$(_EfcptIsSqlProject)' != 'true'";
+    
+    /// <summary>
+    /// Checks if connection string mode is being used.
+    /// </summary>
+    public const string UseConnectionString = "'$(_EfcptUseConnectionString)' == 'true'";
+    
+    /// <summary>
+    /// Checks if direct DACPAC mode is being used.
+    /// </summary>
+    public const string UseDirectDacpac = "'$(_EfcptUseDirectDacpac)' == 'true'";
+    
+    /// <summary>
+    /// Checks if no DACPAC path is specified.
+    /// </summary>
+    public const string NoDacpac = "'$(EfcptDacpac)' == ''";
+    
+    /// <summary>
+    /// Checks if split outputs mode is enabled.
+    /// </summary>
+    public const string SplitOutputs = "'$(EfcptSplitOutputs)' == 'true'";
+    
+    /// <summary>
+    /// Checks if the EFCPT fingerprint has changed.
+    /// </summary>
+    public const string FingerprintChanged = "'$(_EfcptFingerprintChanged)' == 'true'";
+    
+    /// <summary>
+    /// Combines multiple conditions with AND logic.
+    /// </summary>
+    /// <param name="conditions">The conditions to combine.</param>
+    /// <returns>A combined condition string.</returns>
+    public static string And(params string[] conditions) => 
+        string.Join(" and ", conditions);
+    
+    /// <summary>
+    /// Combines multiple conditions with OR logic.
+    /// </summary>
+    /// <param name="conditions">The conditions to combine.</param>
+    /// <returns>A combined condition string.</returns>
+    public static string Or(params string[] conditions) => 
+        string.Join(" or ", conditions);
+    
+    /// <summary>
+    /// Creates a condition that checks if EFCPT is enabled AND another condition is true.
+    /// </summary>
+    /// <param name="condition">The additional condition.</param>
+    /// <returns>A combined condition string.</returns>
+    public static string EfcptEnabledAnd(string condition) => 
+        And(EfcptEnabled, condition);
+    
+    /// <summary>
+    /// Creates a condition for EFCPT-enabled SQL projects.
+    /// </summary>
+    public static string EfcptEnabledSqlProject => 
+        And(EfcptEnabled, IsSqlProject);
+    
+    /// <summary>
+    /// Creates a condition for EFCPT-enabled data access projects (not SQL projects).
+    /// </summary>
+    public static string EfcptEnabledDataAccess => 
+        And(EfcptEnabled, IsNotSqlProject);
+}

src/JD.Efcpt.Build.Definitions/Constants/MSBuildVersions.cs

@@ -0,0 +1,23 @@
+namespace JD.Efcpt.Build.Definitions.Constants;
+
+/// <summary>
+/// MSBuild version constants for task assembly resolution.
+/// Maps MSBuild versions to Visual Studio releases.
+/// </summary>
+public static class MSBuildVersions
+{
+    /// <summary>
+    /// MSBuild 18.0 - Visual Studio 2026 and later
+    /// </summary>
+    public const string VS2026 = "18.0";
+    
+    /// <summary>
+    /// MSBuild 17.14 - Visual Studio 2024 Update 14 and later
+    /// </summary>
+    public const string VS2024Update14 = "17.14";
+    
+    /// <summary>
+    /// MSBuild 17.12 - Visual Studio 2024 Update 12 and later
+    /// </summary>
+    public const string VS2024Update12 = "17.12";
+}

src/JD.Efcpt.Build.Definitions/Registry/UsingTasksRegistry.cs

@@ -0,0 +1,49 @@
+using JD.MSBuild.Fluent.Fluent;
+
+namespace JD.Efcpt.Build.Definitions.Registry;
+
+/// <summary>
+/// Centralized registry for all JD.Efcpt.Build custom MSBuild tasks.
+/// Automatically registers all task assemblies with MSBuild using a data-driven approach.
+/// </summary>
+public static class UsingTasksRegistry
+{
+    /// <summary>
+    /// All custom task names in the JD.Efcpt.Build.Tasks assembly.
+    /// Adding a new task only requires adding its name to this array.
+    /// </summary>
+    private static readonly string[] TaskNames =
+    [
+        "AddSqlFileWarnings",
+        "ApplyConfigOverrides",
+        "CheckSdkVersion",
+        "ComputeFingerprint",
+        "DetectSqlProject",
+        "EnsureDacpacBuilt",
+        "FinalizeBuildProfiling",
+        "InitializeBuildProfiling",
+        "QuerySchemaMetadata",
+        "RenameGeneratedFiles",
+        "ResolveDbContextName",
+        "ResolveSqlProjAndInputs",
+        "RunEfcpt",
+        "RunSqlPackage",
+        "SerializeConfigProperties",
+        "StageEfcptInputs"
+    ];
+    
+    /// <summary>
+    /// Registers all EFCPT custom tasks with MSBuild.
+    /// Uses the resolved task assembly path from SharedPropertyGroups.
+    /// </summary>
+    /// <param name="t">The targets builder to register tasks with.</param>
+    public static void RegisterAll(ITargetsBuilder t)
+    {
+        const string assemblyPath = "$(_EfcptTaskAssembly)";
+        
+        foreach (var taskName in TaskNames)
+        {
+            t.UsingTask($"JD.Efcpt.Build.Tasks.{taskName}", assemblyPath);
+        }
+    }
+}