Replace raw SQL schema with SQLAlchemy Table definitions

[michaelchu]

Move the Chainlit persistence DDL from hand-written SQL strings into
proper SQLAlchemy Table/Column definitions (optopsy/ui/models.py).
metadata.create_all() now emits dialect-appropriate DDL automatically:

• PostgreSQL: UUID, JSONB, TEXT[], BOOLEAN, ON DELETE CASCADE
• SQLite: TEXT, TEXT, TEXT, BOOLEAN (INTEGER affinity), ON DELETE CASCADE

Also aligns with the Chainlit docs schema:

• Add missing columns: steps.command, steps.indent, feedbacks.threadId
• Fix types: feedbacks.value INT (was REAL), elements.page INT (was TEXT)
• Fix nullability: steps.name/type NOT NULL, elements.name NOT NULL
• Add ON DELETE CASCADE to all foreign keys
• Remove stale columns: elements.autoPlay, elements.playerConfig

https://claude.ai/code/session_01M8Tb8gCPXhR6VsExM2KNCm

[Copilot]

Pull request overview

This PR migrates the Chainlit persistence schema from hand-written SQL strings to SQLAlchemy Table/Column definitions so metadata.create_all(engine) can emit dialect-appropriate DDL for SQLite and PostgreSQL.

Changes:

• Add SQLAlchemy Core table definitions for the Chainlit persistence tables (users, threads, steps, elements, feedbacks).
• Replace the raw DDL execution loop in app.py with metadata.create_all(engine) using the new models metadata.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
optopsy/ui/models.py	Introduces SQLAlchemy MetaData + table definitions with dialect variants (UUID/JSONB/ARRAY on Postgres, TEXT fallback on SQLite).
optopsy/ui/app.py	Removes raw SQL schema statements and initializes the DB schema via _db_metadata.create_all(engine).