Enable no-unnecessary-condition lint warnings

[cgasgarth]

Summary

Change	Details
Enable typed lint rule	Enables @typescript-eslint/no-unnecessary-condition as a warning.
Error enforcement	Adds src/hooks/useSortedLibrary.ts to the error-enforced file list.
Remove redundant checks	Removes unnecessary chaining from ImageFile.path and split().
Root config support	Allows i18next.config.ts in the TypeScript project service.

Remaining warnings

Warning type	Count
Unnecessary optional chain	149
Always-truthy conditional	147
Unnecessary ?? fallback	101
Always-falsy conditional	47
Types have no overlap	10
Always-true literal comparison	4
Total	458

Validation

• Production build: passes
• Changed-file formatting: passes
• Selected file: zero no-unnecessary-condition findings
• Full lint/typecheck/i18n checks still report pre-existing repository issues outside this change