fix(data): apply negative feedback filters in SQLAlchemy

[imharjot]

SQLAlchemyDataLayer.list_threads treats feedback=0 as though no feedback filter was supplied. Asking for conversations with thumbs-down feedback therefore returns positively rated and unrated conversations too.

Fixes #3068

Use an explicit None check so zero reaches the existing feedback filter. The seven SQLite regressions check negative, positive and unfiltered results, owner isolation, case-insensitive search and cursor pagination. The fixture retains the original required disableFeedback column and seeds compliant step rows explicitly, while users, feedback writes and thread reads use the real data-layer APIs. It also includes the props column needed by thread reads.

Validation on Python 3.13.16 and Node 24.11.1:

• uv sync --all-packages --all-extras --dev completed, including the frontend build.
• python -m pytest --cov=chainlit using the existing Python 3.13 environment: 939 passed after the review update. With the final fixture and the original feedback filter, the three negative-feedback cases fail and four controls pass.
• From frontend/, pnpm test: 32 frontend tests passed.
• Python lint, formatting and type checks passed; mypy checked all 109 source files.
• pnpm lint, pnpm format-check and pnpm type-check passed. The repository's copilot type-check command explicitly reports that it is skipped.
• pnpm check-overrides passed.
• A local echo app using real SQLite passed login, four WebSocket conversations, HTTP feedback writes and filtered thread-list requests, including search and pagination.
• The two active persistence Cypress cases in cypress/e2e/data_layer/spec.cy.ts passed, with two cases already marked pending in the repository. The first run hit a local server startup race on port 8000. The successful retry used a temporary configuration that waits for the initial server to listen and for cleanup to finish before starting the fixture; the tracked harness and test cases were unchanged.

Local validation covers Python 3.13 and the persistence browser spec; the broader Python and browser matrices remain for CI.

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Summary by cubic

Fixes SQLAlchemyDataLayer.list_threads treating a feedback=0 filter as missing, so requesting thumbs-down conversations returned unrated and positively rated ones too.

• Checks filters.feedback is not None so a zero value reaches the existing feedback filter.
• Adds SQLite regression coverage for negative, positive, and unfiltered results, owner isolation, case-insensitive search, and cursor pagination.

^{Written for commit 272129a. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 2 files

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