Use SQLite as a datastore

[theanmolsharma]

Right now we use Postgres to store the index but using an embedded database such as SQLite makes more sense because of the following reasons:

• No Server Required: SQLite is an embedded database, meaning it runs in the same process as the indexer and doesn't require a separate server to be installed, configured, or managed.
• Zero Configuration: Since SQLite is serverless, it requires no configuration files or startup processes.
• Optimized for Read-Heavy Workloads: SQLite is highly efficient for read-heavy operations, which is typical in indexers that frequently read data to fulfill queries.
• Single File Database: SQLite stores an entire database, including the schema, tables, indexes, and data, in a single file.
• Small Footprint: SQLite has a very small code footprint which makes it ideal for us.

Tasks:

• [ ] Add sqlite as a dependency
• [ ] Install TypeOrm dependencies for SQLite
• [ ] Uninstall Postgress dependencies
• [ ] Update entity if required
• [ ] Miscellaneous changes (updating configs, etc)

The data should be persisted in ~/.silent-pay-indexer/db

[notTanveer]

taking this

[theanmolsharma]

fixed in #30