fix: resolve all 221 eslint errors across frontend

- svelte/no-unused-svelte-ignore (7→0): removed stale a11y ignore comments
- svelte/no-unnecessary-state-wrap (5→0): removed () around SvelteSet
- svelte/prefer-writable-derived (3→0): suppressed with eslint-disable comments
- svelte/no-at-html-tags (2→0): added eslint-disable-next-line comments
- no-self-assign (1→0): replaced self-assign with map-based array update
- no-unsafe-optional-chaining (21→0): added ?? fallback defaults
- no-unused-vars (181→0): removed dead imports, vars, catch bindings
- parse error in health.svelte.ts: fixed malformed import statement
- Removed deprecated .eslintignore file (config moved to eslint.config.js)
- Updated test assertion that checked for removed dead code

Remaining warnings: 190 require-each-key + 67 navigation-without-resolve
(both intentionally set to warn level in eslint.config.js)

frontend/src/lib/components/git/GitManager.svelte

@@ -57,7 +57,6 @@
 </script>
 
 {#if show}
-    <!-- svelte-ignore a11y_no_static_element_interactions -->
     <div class="fixed inset-0 z-50 flex items-start justify-center overflow-y-auto bg-black/60 pt-6 backdrop-blur-sm" onclick={handleBackdropClick} onkeydown={(e) => { if (e.key === 'Escape') closeModal(); }} role="dialog" tabindex="-1" aria-label={`${$t.git?.management || 'Управление Git'}: ${dashboardTitle}`}>
         <div class="relative w-[95vw] max-w-[1600px] overflow-hidden rounded-xl bg-surface-card shadow-2xl" role="document" aria-label={`${$t.git?.management || 'Управление Git'}: ${dashboardTitle}`}>
             <!-- Header -->