Sunshine: use sqlite db for persistent data

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### Is there an existing issue for this item?

- [x] I have searched the existing issues

### Repositories

LizardByte/Sunshine

### Languages/Skills/Technologies

C++, SQL

### Description

I believe it's a better practice to store data in a proper database instead of random json files.

#### Pros
- All data in one location
- Apps can have an actual ID (auto incrementing)
- No more boost json
- Can use db fixtures for unit testing different scenarios
- Can use proper migrations when the db structure changes, storing the db version in migration table... with up and down migrations. For down migrations Sunshine could download the downgrade SQL file from the git repo since it wouldn't be available in the previous versions of Sunshine.

#### Cons
- All data in one location
- SQL

### Estimated Effort

effort:Large

### Priority

priority:Medium

### Target Milestone

6+ months

### Dependencies

_No response_

Start by inventorying Sunshine's current JSON and Boost JSON persistence, then outline the proposed SQLite schema and migration approach. Done means persistent data is consolidated in SQLite, application IDs and migrations are supported, and database fixtures can cover unit-test scenarios.

Written by the indexing model from the issue text.