refactor: introduce domain model classes and mapper layer

Replace ad-hoc inline row casting (snake_case → camelCase) spread across
services, routes, and the indexing pipeline with explicit model classes
(Repository, IndexingJob, RepositoryVersion, Snippet, SearchResult) and
dedicated mapper classes that own the DB → domain conversion.

- Add src/lib/server/models/ with typed model classes for all domain entities
- Add src/lib/server/mappers/ with mapper classes per entity
- Remove duplicated RawRow interfaces and inline map functions from
  job-queue, repository.service, indexing.pipeline, and all API routes
- Add dtoJsonResponse helper to standardise JSON responses via SvelteKit json()
- Add api-contract.integration.test.ts as a regression baseline

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

src/lib/server/services/repository.service.ts

@@ -4,7 +4,10 @@
  */
 
 import type Database from 'better-sqlite3';
-import type { Repository, NewRepository, IndexingJob, NewIndexingJob } from '$lib/types';
+import { RepositoryMapper } from '$lib/server/mappers/repository.mapper.js';
+import { IndexingJobMapper } from '$lib/server/mappers/indexing-job.mapper.js';
+import { Repository, RepositoryEntity } from '$lib/server/models/repository.js';
+import { IndexingJob, IndexingJobEntity } from '$lib/server/models/indexing-job.js';
 import { resolveGitHubId, resolveLocalId } from '$lib/server/utils/id-resolver';
 import {
 	AlreadyExistsError,
@@ -47,16 +50,18 @@ export class RepositoryService {
 		const offset = options?.offset ?? 0;
 
 		if (options?.state) {
-			return this.db
+			const rows = this.db
 				.prepare(
 					`SELECT * FROM repositories WHERE state = ? ORDER BY created_at DESC LIMIT ? OFFSET ?`
 				)
-				.all(options.state, limit, offset) as Repository[];
+				.all(options.state, limit, offset) as RepositoryEntity[];
+			return rows.map((row) => RepositoryMapper.fromEntity(new RepositoryEntity(row)));
 		}
 
-		return this.db
+		const rows = this.db
 			.prepare(`SELECT * FROM repositories ORDER BY created_at DESC LIMIT ? OFFSET ?`)
-			.all(limit, offset) as Repository[];
+			.all(limit, offset) as RepositoryEntity[];
+		return rows.map((row) => RepositoryMapper.fromEntity(new RepositoryEntity(row)));
 	}
 
 	/**
@@ -79,10 +84,10 @@ export class RepositoryService {
 	 * Get a single repository by ID.
 	 */
 	get(id: string): Repository | null {
-		return (
-			(this.db.prepare(`SELECT * FROM repositories WHERE id = ?`).get(id) as Repository | undefined) ??
-			null
-		);
+		const row = this.db.prepare(`SELECT * FROM repositories WHERE id = ?`).get(id) as
+			| RepositoryEntity
+			| undefined;
+		return row ? RepositoryMapper.fromEntity(new RepositoryEntity(row)) : null;
 	}
 
 	/**
@@ -126,24 +131,25 @@ export class RepositoryService {
 		}
 
 		const now = Math.floor(Date.now() / 1000);
-		const repo: Record<string, unknown> = {
+		const repo = new Repository({
 			id,
 			title,
 			description: input.description ?? null,
 			source: input.source,
-			source_url: input.sourceUrl,
+			sourceUrl: input.sourceUrl,
 			branch: input.branch ?? 'main',
 			state: 'pending',
-			total_snippets: 0,
-			total_tokens: 0,
-			trust_score: 0,
-			benchmark_score: 0,
+			totalSnippets: 0,
+			totalTokens: 0,
+			trustScore: 0,
+			benchmarkScore: 0,
 			stars: null,
-			github_token: input.githubToken ?? null,
-			last_indexed_at: null,
-			created_at: now,
-			updated_at: now
-		};
+			githubToken: input.githubToken ?? null,
+			lastIndexedAt: null,
+			createdAt: new Date(now * 1000),
+			updatedAt: new Date(now * 1000)
+		});
+		const entity = RepositoryMapper.toEntity(repo);
 
 		this.db
 			.prepare(
@@ -154,22 +160,22 @@ export class RepositoryService {
          VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`
 			)
 			.run(
-				repo.id,
-				repo.title,
-				repo.description,
-				repo.source,
-				repo.source_url,
-				repo.branch,
-				repo.state,
-				repo.total_snippets,
-				repo.total_tokens,
-				repo.trust_score,
-				repo.benchmark_score,
-				repo.stars,
-				repo.github_token,
-				repo.last_indexed_at,
-				repo.created_at,
-				repo.updated_at
+				entity.id,
+				entity.title,
+				entity.description,
+				entity.source,
+				entity.source_url,
+				entity.branch,
+				entity.state,
+				entity.total_snippets,
+				entity.total_tokens,
+				entity.trust_score,
+				entity.benchmark_score,
+				entity.stars,
+				entity.github_token,
+				entity.last_indexed_at,
+				entity.created_at,
+				entity.updated_at
 			);
 
 		return this.get(id)!;
@@ -274,24 +280,37 @@ export class RepositoryService {
            WHERE repository_id = ? AND status IN ('queued', 'running')
            ORDER BY created_at DESC LIMIT 1`
 			)
-			.get(repositoryId) as IndexingJob | undefined;
+			.get(repositoryId) as IndexingJobEntity | undefined;
 
-		if (runningJob) return runningJob;
+		if (runningJob) return IndexingJobMapper.fromEntity(new IndexingJobEntity(runningJob));
 
 		const now = Math.floor(Date.now() / 1000);
-		const job: Record<string, unknown> = {
+		const job = new IndexingJob({
 			id: crypto.randomUUID(),
-			repository_id: repositoryId,
-			version_id: versionId ?? null,
+			repositoryId,
+			versionId: versionId ?? null,
 			status: 'queued',
 			progress: 0,
-			total_files: 0,
-			processed_files: 0,
+			totalFiles: 0,
+			processedFiles: 0,
 			error: null,
+			startedAt: null,
+			completedAt: null,
+			createdAt: new Date(now * 1000)
+		});
+		const entity = new IndexingJobEntity({
+			id: job.id,
+			repository_id: job.repositoryId,
+			version_id: job.versionId,
+			status: job.status,
+			progress: job.progress,
+			total_files: job.totalFiles,
+			processed_files: job.processedFiles,
+			error: job.error,
 			started_at: null,
 			completed_at: null,
 			created_at: now
-		};
+		});
 
 		this.db
 			.prepare(
@@ -301,21 +320,22 @@ export class RepositoryService {
          VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`
 			)
 			.run(
-				job.id,
-				job.repository_id,
-				job.version_id,
-				job.status,
-				job.progress,
-				job.total_files,
-				job.processed_files,
-				job.error,
-				job.started_at,
-				job.completed_at,
-				job.created_at
+				entity.id,
+				entity.repository_id,
+				entity.version_id,
+				entity.status,
+				entity.progress,
+				entity.total_files,
+				entity.processed_files,
+				entity.error,
+				entity.started_at,
+				entity.completed_at,
+				entity.created_at
 			);
 
-		return this.db
+		const created = this.db
 			.prepare(`SELECT * FROM indexing_jobs WHERE id = ?`)
-			.get(job.id) as IndexingJob;
+			.get(job.id) as IndexingJobEntity;
+		return IndexingJobMapper.fromEntity(new IndexingJobEntity(created));
 	}
 }