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/server/models/embedding-settings.ts

@@ -0,0 +1,20 @@
+import type { EmbeddingProfile } from './embedding-profile.js';
+
+export interface EmbeddingSettingsProps {
+	profiles: EmbeddingProfile[];
+	activeProfile: EmbeddingProfile | null;
+}
+
+export class EmbeddingSettings {
+	profiles: EmbeddingProfile[];
+	activeProfile: EmbeddingProfile | null;
+
+	constructor(props: EmbeddingSettingsProps) {
+		this.profiles = props.profiles;
+		this.activeProfile = props.activeProfile;
+	}
+
+	get activeProfileId(): string | null {
+		return this.activeProfile?.id ?? null;
+	}
+}