feat(EMBEDDINGS-0001): enable local embedder by default and overhaul settings page

- Wire local embedding provider as the default on startup when no profile is configured
- Refactor embedding settings into dedicated service, DTOs, mappers and models
- Rebuild settings page with profile management UI and live test feedback
- Expose index summary (indexed versions + embedding count) on repo endpoints
- Harden indexing pipeline and context search with additional test coverage

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

src/lib/components/RepositoryCard.svelte.test.ts

@@ -12,6 +12,8 @@ describe('RepositoryCard.svelte', () => {
 				description: 'A JavaScript library for building user interfaces',
 				state: 'indexed',
 				totalSnippets: 1234,
+				embeddingCount: 1200,
+				indexedVersions: ['main', 'v18.3.0'],
 				trustScore: 9.7,
 				stars: 230000,
 				lastIndexedAt: null
@@ -23,5 +25,8 @@ describe('RepositoryCard.svelte', () => {
 		await expect
 			.element(page.getByRole('link', { name: 'Details' }))
 			.toHaveAttribute('href', '/repos/%2Ffacebook%2Freact');
+
+		await expect.element(page.getByText('1,200 embeddings')).toBeInTheDocument();
+		await expect.element(page.getByText('Indexed: main, v18.3.0')).toBeInTheDocument();
 	});
 });