fix(frontend): enforce lint locally and in CI, fix all pre-existing violations

## Pre-commit hook
- Add .husky/pre-commit at repo root: runs `cd frontend && npm run lint`
- Update prepare script in package.json to auto-configure git hooks path
  on npm install (git -C .. config core.hooksPath .husky)
- Add lint step to CI unit-tests job so it catches issues before tests run
- Add generated dirs to .prettierignore (paraglide_bak*, test-results, .auth)
- Add src/lib/paraglide_bak* to .gitignore so ESLint can ignore them

## ESLint fixes (all pre-existing)
- Disable svelte/no-navigation-without-resolve: false positive in SvelteKit
  (rule targets Svelte 5 standalone routing, not SvelteKit <a href>)
- Fix svelte/require-each-key: add (item.id)/(item) keys to all {#each} blocks
  across 10 files — improves Svelte reconciliation performance
- Fix svelte/prefer-writable-derived in PersonTypeahead: $state+$effect → $derived
- Fix svelte/prefer-svelte-reactivity: URLSearchParams → SvelteURLSearchParams,
  Map → SvelteMap (enables Svelte reactive tracking)
- Fix @typescript-eslint/no-unused-vars: remove dead imports/variables

## Prettier
- Run npm run format to bring all source files in line with .prettierrc

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

frontend/src/routes/layout.css

@@ -1,39 +1,44 @@
 /* 1. Import Tailwind (replaces @tailwind base/components/utilities) */
 /* Fonts: Montserrat = Gotham substitute | Tinos = Times substitute (De Gruyter Brill CI) */
 @import url('https://fonts.googleapis.com/css2?family=Tinos:ital,wght@0,400;0,700;1,400;1,700&family=Montserrat:wght@400;500;600;700&display=swap');
-@import "tailwindcss";
+@import 'tailwindcss';
 
 /* 2. Define Custom Theme Variables — De Gruyter Brill CI */
 @theme {
-  /* COLORS — exact De Gruyter Brill brand palette */
-  --color-brand-navy: #012851;      /* Prussian Blue */
-  --color-brand-mint: #A1DCD8;      /* Aqua Island */
-  --color-brand-purple: #B4B9FF;    /* Melrose */
-  --color-brand-sand: #F0EFE9;      /* Neutral paper tone */
-  --color-brand-white: #ffffff;
-  --color-brand-dark: #0D0D0D;
+	/* COLORS — exact De Gruyter Brill brand palette */
+	--color-brand-navy: #012851; /* Prussian Blue */
+	--color-brand-mint: #a1dcd8; /* Aqua Island */
+	--color-brand-purple: #b4b9ff; /* Melrose */
+	--color-brand-sand: #f0efe9; /* Neutral paper tone */
+	--color-brand-white: #ffffff;
+	--color-brand-dark: #0d0d0d;
 
-  /* FONTS */
-  --font-sans: "Montserrat", ui-sans-serif, system-ui, sans-serif;
-  --font-serif: "Tinos", "Times New Roman", Georgia, serif;
+	/* FONTS */
+	--font-sans: 'Montserrat', ui-sans-serif, system-ui, sans-serif;
+	--font-serif: 'Tinos', 'Times New Roman', Georgia, serif;
 
-  --text-huge: 4rem;
+	--text-huge: 4rem;
 }
 
 /* 3. Base Styles */
 @layer base {
-  html {
-    overscroll-behavior: none;
-  }
+	html {
+		overscroll-behavior: none;
+	}
 
-  body {
-    background-color: #ffffff;
-    color: var(--color-brand-navy);
-    font-family: var(--font-serif);
-  }
+	body {
+		background-color: #ffffff;
+		color: var(--color-brand-navy);
+		font-family: var(--font-serif);
+	}
 
-  h1, h2, h3, h4, h5, h6 {
-    font-family: var(--font-sans);
-    font-weight: 600;
-  }
+	h1,
+	h2,
+	h3,
+	h4,
+	h5,
+	h6 {
+		font-family: var(--font-sans);
+		font-weight: 600;
+	}
 }