v3.0.4 - Address PR #2 review feedback + capture Tesseract stderr + complete ISystemEnvironment abstraction + CI hygiene

Bundles PRs #3, #5, #6, #7, #8 that all landed at the 3.0.3 version label.
Contents are bug fixes and internal refactoring only — no public API
changes, no breaking behavior:

- #3  Address Copilot review comments from PR #2
      - TesseractOcrProvider.ExtractTextFromImageAsync derives the actual
        .txt path Tesseract writes (not the caller's input path)
      - OcrService.TryDeleteDirectory is now truly best-effort
        (catch (IOException or UnauthorizedAccessException))
- #5  Capture Tesseract stderr in OCR-failure exception message
      - New internal ProcessResult record struct
      - IProcessRunner.RunAsync now returns Task<ProcessResult>
      - ProcessRunner reads stdout + stderr concurrently to avoid the
        full-pipe deadlock
- #6  Finish ISystemEnvironment abstraction
      - ISystemEnvironment.ReadAllTextAsync added so the success branch is
        unit-testable without touching the real filesystem
- #7  CI hygiene
      - nuget-publish.yml: install Pillow before the icon-optimisation
        Python heredoc (was failing with ModuleNotFoundError)
      - DocumentTests.FluentApi: Guid-suffixed filename so parallel
        TFM hosts do not race on output/fluent-test.pdf
- #8  Clean up nuspec dependency groups (NU5128)
      - Drop SuppressDependenciesWhenPacking + dead NU5128 NoWarn
      - dotnet pack now emits canonical empty <group> per TFM

Tests: 256/256 pass per TFM × net8.0/net9.0/net10.0
Coverage: 100% line, 97.42% branch
Pack: 0 warnings, 0 errors

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ANcpLua

CreatePdf.NET/CreatePdf.NET.csproj

@@ -7,7 +7,7 @@
 
     <PackageId>CreatePdf.NET</PackageId>
     <Title>CreatePdf.NET - Simple PDF Creation Library</Title>
-    <Version>3.0.3</Version>
+    <Version>3.0.4</Version>
     <Authors>Alexander Nachtmann</Authors>
     <Summary>Lightweight PDF generation library for .NET 10/9/8 with text rendering, bitmap graphics, and OCR</Summary>
     <Description>CreatePdf.NET is a simple, fast PDF creation library for .NET applications. Generate PDF documents with text rendering, bitmap graphics, and optional OCR text extraction. Lightweight, dependency-free, 100% test coverage. Perfect for creating reports, invoices, receipts, labels, and documents. Supports .NET 10, .NET 9, and .NET 8 with fluent C# API.</Description>