feat(backend): add database schema and setup prisma service

[ahonn]

DB design draft: https://www.notion.so/DB-design-36446d3dd8784e2bbc77c1e7db97d594#fe5eee86ba194cc0b64a4d22ff0b38a5

Some modifications(d52b2f3 , f91b194) were made based on the table structure in the draft:

• Use Timestamp in Postgresql as the timestamp field type
• Add the epoch field to the blocks table
• Add blockId field to the blocks table
• Add the TransactionStatus enum and status field to the transactions table
• Rename generatedByTxId field to txId in outputs table
• Rename content/contentSize to data/dataSize in outputs table
• Rename accounts table to balances and remove account_no field
• Add foreign keys to tables and use id to establish relations