feat: add modular services and repositories for improved code organization

Introduce repository pattern across multiple services, including `favorites`, `tags`, `sessions`, `reports`, `auth`, and more. Decouple crypto functionalities into modular services like `HashingService`, `JwtService`, and `EncryptionService`. Improve testability and maintainability by simplifying dependencies and consolidating utility logic.

backend/src/reports/repositories/reports.repository.ts

@@ -0,0 +1,50 @@
+import { Injectable } from "@nestjs/common";
+import { desc, eq, lte } from "drizzle-orm";
+import { DatabaseService } from "../../database/database.service";
+import { reports } from "../../database/schemas";
+
+@Injectable()
+export class ReportsRepository {
+	constructor(private readonly databaseService: DatabaseService) {}
+
+	async create(data: {
+		reporterId: string;
+		contentId?: string;
+		tagId?: string;
+		reason: string;
+		description?: string;
+	}) {
+		const [newReport] = await this.databaseService.db
+			.insert(reports)
+			.values(data)
+			.returning();
+		return newReport;
+	}
+
+	async findAll(limit: number, offset: number) {
+		return await this.databaseService.db
+			.select()
+			.from(reports)
+			.orderBy(desc(reports.createdAt))
+			.limit(limit)
+			.offset(offset);
+	}
+
+	async updateStatus(
+		id: string,
+		status: "pending" | "reviewed" | "resolved" | "dismissed",
+	) {
+		return await this.databaseService.db
+			.update(reports)
+			.set({ status, updatedAt: new Date() })
+			.where(eq(reports.id, id))
+			.returning();
+	}
+
+	async purgeObsolete(now: Date) {
+		return await this.databaseService.db
+			.delete(reports)
+			.where(lte(reports.expiresAt, now))
+			.returning();
+	}
+}