[Due for payment 2025-06-02] Clean up and formalise patch management

[mountiny]

Problem

Over time, our ./patches directory has grown to include over 110 files.

Managing such a large collection has become increasingly difficult, particularly during dependency upgrades (e.g., react-native). It is often unclear whether a given patch is still necessary or when it was originally introduced. Tracing its origin typically requires digging through GitHub history, as blame often fails to link back to the original pull request, especially after file renames.

Solution

Restructure the patches directory into subdirectories based on the target library:

patches/
├── react-native-pdf/
│   ├── details.md
│   ├── react-native-pdf+6.7.3+001+initial.patch
│   ├── react-native-pdf+6.7.3+002+fix-incorrect-decoding.patch
│   └── react-native-pdf+6.7.3+003+update-podspec.patch

├── react-native/
│   ├── details.md
│   ├── patch1.patch
│   └── ...

Each details.md file would contain a table (exact format to be discussed) listing each patch, the rationale for its introduction, and links to both the app-level and upstream pull requests.

Additionally, we would require contributors to update the corresponding details.md file whenever a patch is added or modified. This will ensure that all patches are documented and will encourage the creation of upstream pull requests, which is currently rare

Issue Owner

Current Issue Owner: @dylanexpensify

[melvin-bot]

Triggered auto assignment to @dylanexpensify (NewFeature), see https://stackoverflowteams.com/c/expensify/questions/14418#:~:text=BugZero%20process%20steps%20for%20feature%20requests for more details. Please add this Feature request to a GH project, as outlined in the SO.

[mountiny]

@war-in lets laso add the gh action