Fix linting errors across backend and frontend

Backend: auto-fix and format all ruff issues, manually fix B904/B023/
SIM117/B007/E741/F841 errors, suppress B008 (FastAPI Depends) and F821
(SQLAlchemy forward refs) in config. Frontend: allow constant exports,
disable React compiler-specific rules (set-state-in-effect,
preserve-manual-memoization).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.beans/nuzlocke-tracker-ve9f--fix-linting-errors-across-backend-and-frontend.md

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+---
+# nuzlocke-tracker-ve9f
+title: Fix linting errors across backend and frontend
+status: in-progress
+type: task
+priority: normal
+created_at: 2026-02-10T11:21:24Z
+updated_at: 2026-02-10T11:22:42Z
+---
+
+The CI pipeline is now running but linting fails on both backend and frontend. Clean up all lint errors so CI passes green.
+
+## Backend (ruff)
+
+- **236 errors** found, **126 auto-fixable** with `ruff check --fix`
+- **44 files** need reformatting with `ruff format`
+- Most issues are in alembic migrations (auto-generated boilerplate: `Union` → `X | Y`, import sorting, unused imports) and across API/model/seed files (formatting, datetime.UTC, loop variable issues)
+- Fix approach:
+  1. Run `ruff check --fix backend/` to auto-fix 126 issues
+  2. Run `ruff format backend/` to reformat 44 files
+  3. Manually fix remaining ~110 issues (B023 loop variable binding, SIM117, etc.)
+
+## Frontend (eslint + tsc)
+
+- Run `cd frontend && npm ci && npm run lint` to see errors
+- Run `npx tsc -b` for type checking
+- Fix any reported issues
+
+## Checklist
+
+- [x] Auto-fix backend ruff lint errors (`ruff check --fix backend/`)
+- [x] Auto-format backend files (`ruff format backend/`)
+- [x] Manually fix remaining backend lint errors
+- [x] Fix frontend eslint errors
+- [x] Fix frontend TypeScript errors (if any)
+- [ ] Verify CI passes green on develop