[rd-code-23]

Problem

Routine building needs a persistent exercise catalog that can represent both globally available built-in exercises and custom exercises owned by a registered user.

What changed

• Added the Drizzle exercises table schema.
• Exported the table from the complete database schema index.
• Generated migration 0002_illegal_captain_flint.sql.
• Added the generated Drizzle snapshot and journal entry.
• Added concise field comments explaining each column's product responsibility.

Table design

The table contains:

• id: generated UUID primary key
• owner_user_id: nullable foreign key to users.id
• name: required exercise name
• description: optional instructions or explanation
• created_at and updated_at: timezone-aware timestamps with defaults

Ownership is represented intentionally:

• owner_user_id IS NULL means the exercise is built into GoForLift.
• A user ID means the exercise is a custom exercise owned by that user.

The foreign key uses PostgreSQL's default NO ACTION deletion behavior. Deleting a user therefore cannot silently cascade-delete exercise records. Account and exercise deletion behavior can be finalized deliberately when those operations are implemented.

An index on owner_user_id supports looking up a user's custom exercises and separating them from built-in catalog entries. No speculative name uniqueness rule or additional indexes were added because those requirements are not yet established.

Scope

This PR implements only #54.

Out of scope:

• built-in exercise seed data
• exercise CRUD endpoints
• routine tables
• routine UI
• guest persistence
• workout history tables

Migration verification

After generating the migration, Drizzle detected three tables and reported the expected exercises shape: six columns, one index, and one foreign key. A second generation reported No schema changes, nothing to migrate, confirming the schema and metadata are consistent.

Verification

• pnpm --filter @goforlift/api typecheck
• pnpm --filter @goforlift/api test — 48 tests passed
• pnpm --filter @goforlift/api lint
• Prettier checks for changed schema and generated metadata
• git diff --check

The migration is committed but was not applied to a developer's local PostgreSQL database as part of this PR.

Closes #54