[M0-2] Feat: Database schema skeleton

[ajstrongdev]

This pull request significantly expands and restructures the database schema by introducing new tables and defining their relationships. The changes lay the groundwork for handling accounts, access tokens, politicians, nations, and statistics, replacing the previous single todos table with a more comprehensive data model.

Database schema expansion and restructuring:

• Added new tables: accounts, accessTokens, politicians, nations, and stats, each with relevant fields and constraints to support user accounts, authentication tokens, political roles, nations, and per-nation statistics.
• Removed the old todos table, reflecting a shift away from a simple to-do model to a more complex domain.

Relations and data integrity:

• Defined relations between tables using the relations helper, including:
  • Accounts to their politicians and access tokens.
  • Access tokens to their creator and redeemer accounts.
  • Nations to their statistics and politicians.
  • Politicians to their associated account and nation.
  • Stats to their nation.