Integrate Roslyn code analysis into build pipeline #46

Overview

Add Roslyn-based static code analysis to catch bugs at compile time. The infrastructure is already partially wired up (FxCopAnalyzers referenced but disabled).

Sub-tasks

• Tier 1: Enable built-in .NET analyzers and configure severity #47 — Tier 1: Enable built-in .NET analyzers (replace deprecated FxCopAnalyzers, configure severity)
• Tier 2: Add Roslynator.Analyzers for broader code quality #48 — Tier 2: Add Roslynator.Analyzers for broader code quality coverage
• Tier 3: Custom ConfuserEx-specific Roslyn analyzers #49 — Tier 3: Create custom ConfuserEx-specific analyzers (CX001-CX004)

Context

Many bugs fixed in this pre-release cycle (ResolveThrow crashes, typeof().GetMethod() mscorlib mismatch, unhandled ReflectionTypeLoadException) could be caught automatically by analyzers.