Align repo config with global development standards

- Add missing tsconfig strictness flags (noUncheckedIndexedAccess,
  exactOptionalPropertyTypes, noImplicitOverride,
  noPropertyAccessFromIndexSignature) and fix all resulting type errors
- Replace ESLint/Prettier with oxlint 1.48.0 and oxfmt 0.33.0
- Pin all frontend and backend dependencies to exact versions
- Pin GitHub Actions to SHA hashes with persist-credentials: false
- Fix CI Python version mismatch (3.12 -> 3.14) and ruff target-version
- Add vitest 4.0.18 with jsdom environment for frontend testing
- Add ty 0.0.17 for Python type checking (non-blocking in CI)
- Add actionlint and zizmor CI job for workflow linting and security audit
- Add Dependabot config for npm, pip, and github-actions
- Update CLAUDE.md and pre-commit hooks to reflect new tooling
- Ignore Claude Code sandbox artifacts in gitignore

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

.pre-commit-config.yaml

@@ -12,18 +12,18 @@ repos:
   # Frontend (TypeScript/React) — local hooks using project node_modules
   - repo: local
     hooks:
-      - id: eslint
-        name: eslint
-        entry: npx eslint
+      - id: oxlint
+        name: oxlint
+        entry: npx oxlint -c frontend/.oxlintrc.json
         language: system
         files: ^frontend/src/.*\.(ts|tsx)$
         pass_filenames: true
 
-      - id: prettier
-        name: prettier
-        entry: npx prettier --check
+      - id: oxfmt
+        name: oxfmt
+        entry: npx oxfmt --check --config frontend/.oxfmtrc.json
         language: system
-        files: ^frontend/src/.*\.(ts|tsx|css|json)$
+        files: ^frontend/src/.*\.(ts|tsx)$
         pass_filenames: true
 
       - id: tsc