feat(crypto): Complete Phase 2 - Configuration-driven crypto architecture with 100% compliance

## Summary

This commit completes Phase 2 of the configuration-driven crypto architecture, achieving
100% crypto compliance by eliminating all hardcoded cryptographic implementations.

## Key Changes

### Phase 1: Plugin Loader Infrastructure
- **Plugin Discovery System**: Created StellaOps.Cryptography.PluginLoader with manifest-based loading
- **Configuration Model**: Added CryptoPluginConfiguration with regional profiles support
- **Dependency Injection**: Extended DI to support plugin-based crypto provider registration
- **Regional Configs**: Created appsettings.crypto.{international,russia,eu,china}.yaml
- **CI Workflow**: Added .gitea/workflows/crypto-compliance.yml for audit enforcement

### Phase 2: Code Refactoring
- **API Extension**: Added ICryptoProvider.CreateEphemeralVerifier for verification-only scenarios
- **Plugin Implementation**: Created OfflineVerificationCryptoProvider with ephemeral verifier support
  - Supports ES256/384/512, RS256/384/512, PS256/384/512
  - SubjectPublicKeyInfo (SPKI) public key format
- **100% Compliance**: Refactored DsseVerifier to remove all BouncyCastle cryptographic usage
- **Unit Tests**: Created OfflineVerificationProviderTests with 39 passing tests
- **Documentation**: Created comprehensive security guide at docs/security/offline-verification-crypto-provider.md
- **Audit Infrastructure**: Created scripts/audit-crypto-usage.ps1 for static analysis

### Testing Infrastructure (TestKit)
- **Determinism Gate**: Created DeterminismGate for reproducibility validation
- **Test Fixtures**: Added PostgresFixture and ValkeyFixture using Testcontainers
- **Traits System**: Implemented test lane attributes for parallel CI execution
- **JSON Assertions**: Added CanonicalJsonAssert for deterministic JSON comparisons
- **Test Lanes**: Created test-lanes.yml workflow for parallel test execution

### Documentation
- **Architecture**: Created CRYPTO_CONFIGURATION_DRIVEN_ARCHITECTURE.md master plan
- **Sprint Tracking**: Created SPRINT_1000_0007_0002_crypto_refactoring.md (COMPLETE)
- **API Documentation**: Updated docs2/cli/crypto-plugins.md and crypto.md
- **Testing Strategy**: Created testing strategy documents in docs/implplan/SPRINT_5100_0007_*

## Compliance & Testing

- ✅ Zero direct System.Security.Cryptography usage in production code
- ✅ All crypto operations go through ICryptoProvider abstraction
- ✅ 39/39 unit tests passing for OfflineVerificationCryptoProvider
- ✅ Build successful (AirGap, Crypto plugin, DI infrastructure)
- ✅ Audit script validates crypto boundaries

## Files Modified

**Core Crypto Infrastructure:**
- src/__Libraries/StellaOps.Cryptography/CryptoProvider.cs (API extension)
- src/__Libraries/StellaOps.Cryptography/CryptoSigningKey.cs (verification-only constructor)
- src/__Libraries/StellaOps.Cryptography/EcdsaSigner.cs (fixed ephemeral verifier)

**Plugin Implementation:**
- src/__Libraries/StellaOps.Cryptography.Plugin.OfflineVerification/ (new)
- src/__Libraries/StellaOps.Cryptography.PluginLoader/ (new)

**Production Code Refactoring:**
- src/AirGap/StellaOps.AirGap.Importer/Validation/DsseVerifier.cs (100% compliant)

**Tests:**
- src/__Libraries/__Tests/StellaOps.Cryptography.Plugin.OfflineVerification.Tests/ (new, 39 tests)
- src/__Libraries/__Tests/StellaOps.Cryptography.PluginLoader.Tests/ (new)

**Configuration:**
- etc/crypto-plugins-manifest.json (plugin registry)
- etc/appsettings.crypto.*.yaml (regional profiles)

**Documentation:**
- docs/security/offline-verification-crypto-provider.md (600+ lines)
- docs/implplan/CRYPTO_CONFIGURATION_DRIVEN_ARCHITECTURE.md (master plan)
- docs/implplan/SPRINT_1000_0007_0002_crypto_refactoring.md (Phase 2 complete)

## Next Steps

Phase 3: Docker & CI/CD Integration
- Create multi-stage Dockerfiles with all plugins
- Build regional Docker Compose files
- Implement runtime configuration selection
- Add deployment validation scripts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/__Libraries/StellaOps.TestKit/Fixtures/PostgresFixture.cs

@@ -0,0 +1,106 @@
+using Testcontainers.PostgreSql;
+using Xunit;
+
+namespace StellaOps.TestKit.Fixtures;
+
+/// <summary>
+/// Test fixture for PostgreSQL database using Testcontainers.
+/// Provides an isolated PostgreSQL instance for integration tests.
+/// </summary>
+public sealed class PostgresFixture : IAsyncLifetime
+{
+    private readonly PostgreSqlContainer _container;
+
+    public PostgresFixture()
+    {
+        _container = new PostgreSqlBuilder()
+            .WithImage("postgres:16-alpine")
+            .WithDatabase("testdb")
+            .WithUsername("testuser")
+            .WithPassword("testpass")
+            .Build();
+    }
+
+    /// <summary>
+    /// Gets the connection string for the PostgreSQL container.
+    /// </summary>
+    public string ConnectionString => _container.GetConnectionString();
+
+    /// <summary>
+    /// Gets the database name.
+    /// </summary>
+    public string DatabaseName => "testdb";
+
+    /// <summary>
+    /// Gets the hostname of the PostgreSQL container.
+    /// </summary>
+    public string Host => _container.Hostname;
+
+    /// <summary>
+    /// Gets the exposed port of the PostgreSQL container.
+    /// </summary>
+    public ushort Port => _container.GetMappedPublicPort(5432);
+
+    public async Task InitializeAsync()
+    {
+        await _container.StartAsync();
+    }
+
+    public async Task DisposeAsync()
+    {
+        await _container.DisposeAsync();
+    }
+
+    /// <summary>
+    /// Executes a SQL command against the database.
+    /// </summary>
+    public async Task ExecuteSqlAsync(string sql)
+    {
+        await using var conn = new Npgsql.NpgsqlConnection(ConnectionString);
+        await conn.OpenAsync();
+
+        await using var cmd = new Npgsql.NpgsqlCommand(sql, conn);
+        await cmd.ExecuteNonQueryAsync();
+    }
+
+    /// <summary>
+    /// Creates a new database within the container.
+    /// </summary>
+    public async Task CreateDatabaseAsync(string databaseName)
+    {
+        var createDbSql = $"CREATE DATABASE {databaseName}";
+        await ExecuteSqlAsync(createDbSql);
+    }
+
+    /// <summary>
+    /// Drops a database within the container.
+    /// </summary>
+    public async Task DropDatabaseAsync(string databaseName)
+    {
+        var dropDbSql = $"DROP DATABASE IF EXISTS {databaseName}";
+        await ExecuteSqlAsync(dropDbSql);
+    }
+
+    /// <summary>
+    /// Gets a connection string for a specific database in the container.
+    /// </summary>
+    public string GetConnectionString(string databaseName)
+    {
+        var builder = new Npgsql.NpgsqlConnectionStringBuilder(ConnectionString)
+        {
+            Database = databaseName
+        };
+        return builder.ToString();
+    }
+}
+
+/// <summary>
+/// Collection fixture for PostgreSQL to share the container across multiple test classes.
+/// </summary>
+[CollectionDefinition("Postgres")]
+public class PostgresCollection : ICollectionFixture<PostgresFixture>
+{
+    // This class has no code, and is never created. Its purpose is simply
+    // to be the place to apply [CollectionDefinition] and all the
+    // ICollectionFixture<> interfaces.
+}

src/__Libraries/StellaOps.TestKit/Fixtures/ValkeyFixture.cs

@@ -0,0 +1,56 @@
+using Testcontainers.Redis;
+using Xunit;
+
+namespace StellaOps.TestKit.Fixtures;
+
+/// <summary>
+/// Test fixture for Valkey (Redis-compatible) using Testcontainers.
+/// Provides an isolated Valkey instance for integration tests.
+/// </summary>
+public sealed class ValkeyFixture : IAsyncLifetime
+{
+    private readonly RedisContainer _container;
+
+    public ValkeyFixture()
+    {
+        _container = new RedisBuilder()
+            .WithImage("valkey/valkey:8-alpine")
+            .Build();
+    }
+
+    /// <summary>
+    /// Gets the connection string for the Valkey container.
+    /// </summary>
+    public string ConnectionString => _container.GetConnectionString();
+
+    /// <summary>
+    /// Gets the hostname of the Valkey container.
+    /// </summary>
+    public string Host => _container.Hostname;
+
+    /// <summary>
+    /// Gets the exposed port of the Valkey container.
+    /// </summary>
+    public ushort Port => _container.GetMappedPublicPort(6379);
+
+    public async Task InitializeAsync()
+    {
+        await _container.StartAsync();
+    }
+
+    public async Task DisposeAsync()
+    {
+        await _container.DisposeAsync();
+    }
+}
+
+/// <summary>
+/// Collection fixture for Valkey to share the container across multiple test classes.
+/// </summary>
+[CollectionDefinition("Valkey")]
+public class ValkeyCollection : ICollectionFixture<ValkeyFixture>
+{
+    // This class has no code, and is never created. Its purpose is simply
+    // to be the place to apply [CollectionDefinition] and all the
+    // ICollectionFixture<> interfaces.
+}