Add initial db migration for fresh setups

[pstamatop]

Adds an initial “baseline” migration containing the full DB schema.
This migration is timestamped earlier than all others so new environments can be bootstrapped using migrations alone (with synchronize: false).

• Environments that already have data must not run the InitSchema migration, because their schema already exists.
  Instead, they should mark it as executed without running it:

Option A (inside wallet-backend-server container):

yarn typeorm migration:run --fake

Option B (inside wallet-db):

INSERT INTO migrations (timestamp, name)
VALUES (1762258689036, 'InitSchema1762258689036');

After this baseline step, all future migrations will apply normally.

• Fresh clones only need to run

yarn typeorm migration:run

which will create the full schema and then apply later migrations.