[Chapters] Parse toc and modify index

[danielebogo]

This PR introduces filtering out chapters that should not be in the table of contents. See the specification for more details.

The implementation relies on splitting real index and UI index. Real index is stored and is always used for syncing pre-selected chapters. While UI index is computed on-the-fly after we filter out all invalid chapters, etc.

In the database migration I had to delete all cached remote chapters as we don't have information whether such chapters should be displayed or not.

To test

1. Install the app from the main branch.
2. Subscribe to the No Agenda podcast.
3. Play the 1728 - "Hatchet Man" - No Agenda episode.
4. See chapters.
5. Deselect a chapter like X sats from Y.
6. Close the app.
7. Install the app from task/chaptes-toc branch.
8. Go back to the chapters from the 4th step.
9. Verify that you don't see X sats from Y chapters and no chapters got de-selected.

Checklist

• I have considered if this change warrants user-facing release notes and have added them to CHANGELOG.md if necessary.
• I have considered adding unit tests for my changes.
• I have updated (or requested that someone edit) the spreadsheet to reflect any new or changed analytics.

[SergioEstevao]

Followed the PR test steps and all is working correctly:

• Only toc chapters were visible
• None was deselected because toc hidden chapters were deselected on the original branch

[leandroalonso]

@danielebogo chapters are not skipping as they should. Here's the test I did:

1. Went on develop and deselected some chapters
2. Ran this branch/app
3. Tap play
4. Once the chapter "Fire by climate" finishes I expected "New uniform" to play. It didn't, it just ket playing, as you can see below:

Simulator.Screen.Recording.-.iPhone.16.Pro.-.2025-03-11.at.16.44.53.mp4

[pocketcasts]

Version 7.85 has now entered code-freeze, so the milestone of this PR has been updated to 7.86.