Re-enable `noPropertyAccessFromIndexSignature` TypeScript strict option in app

[claude]

Background

In PR #2676, we updated frontend/apps/app/tsconfig.json to use a shared base configuration. To avoid extensive codebase changes during the migration, we temporarily disabled the noPropertyAccessFromIndexSignature TypeScript compiler option.

What is noPropertyAccessFromIndexSignature?

This TypeScript compiler option requires you to use bracket notation (obj['property']) instead of dot notation (obj.property) when accessing properties that don't exist in the type definition but are allowed by an index signature.

When enabled, it prevents runtime errors by forcing explicit acknowledgment that you're accessing potentially undefined properties.

Task

Re-enable the noPropertyAccessFromIndexSignature option in frontend/apps/app/tsconfig.json by:

1. Audit the codebase - Find all locations where dot notation is used to access index signature properties
2. Fix violations - Update code to use bracket notation or improve type definitions where appropriate
3. Remove the override - Remove "noPropertyAccessFromIndexSignature": false from the tsconfig.json compiler options
4. Verify - Ensure all TypeScript compilation passes with the option enabled

References

• Related PR: feat: use shared TypeScript base config for app tsconfig.json #2676
• TypeScript Handbook: Index Signatures

[github-actions]

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