OpenReader: äldre versioner att ladda ner

## OpenReader v1.2.7 — Phase 1 Windows Integration

### Windows file integration
OpenReader now appears under **Open with**
OpenReader now appears in **Default apps**
`.pdf` file-association registration is corrected (MSIX `windows.fileTypeAssociation` + Inno `ChangesAssociations=yes`)
Opening additional PDFs routes them into the existing OpenReader instance
Improved handling for paths with spaces, Unicode filenames, parentheses, and long paths

### Default PDF reader experience
First-launch default-reader prompt (Set as default / Maybe later / Do not ask again)
Settings section for PDF defaults (**File → Settings → Files / Default Apps**)
Accurate detection of OpenReader as the current default (ownership resolved via the registered open command / AppUserModelId across HKCU + HKLM)
Direct access to Windows Default Apps
No silent takeover of Windows defaults

### Store-aware updates
Microsoft Store / MSIX installs use the Store update experience (Open Microsoft Store, no GitHub redirect)
GitHub / Inno installs retain GitHub release checks
Portable and development installs receive appropriate update handling
Improved offline behavior (clean error message + Try Again)
Persisted skip-version support

### Maintenance
Version-source alignment (single source of truth: `main.py`, MCP package metadata, MSIX manifests)
Changelog cleanup
Improved packaging tests
Expanded Windows integration and path-handling coverage

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### Assets

| Asset | Size | SHA-256 |
|---|---|---|
| `OpenReader-Setup.exe` | 54,712,057 | `9c2f1832369ffdc277097c3ebf78c3c3299d0c5d6c771f6459b501d6bc00dc9b` |
| `OpenReader.msix` | 83,287,899 | `2d696c86dcdf1dc9821085e8d95f335a553b2059f125c8384232b3cc3e4f431e` |
| `OpenReader-Windows.zip` | 82,375,222 | `6752b4d54ab83cd190430bef9c6a6821ac41e093c7cd76ad34ccc3732f91bf5a` |
| `OpenReader-macOS-Apple-Silicon.zip` | 67,145,839 | — |
| `OpenReader-macOS-Intel.zip` | 72,711,149 | — |

The MSIX package is unsigned for sideloading (requires Windows Developer Mode) and carries the frozen identity `SparshSam.OpenReader` at version `1.2.7.0`. Microsoft Store signing is applied at submission.