Move from JSON to SQLite

[someretical]

Is your feature request related to a problem? Please describe. Not really related to a problem but more to do with optimization.

Describe the solution you'd like Move to using SQLite to store the diary.

• This removes the need for my own custom structs
• SQLite has backwards compatibility
• SQLite already implements its own caching and compression
• SQLite is lightweight

Describe alternatives you've considered None

Additional context The SQLite database must be serialised and de-serialised in memory since it must then be encrypted. Qt already has SQLite bindings.