feat(zkp): implement ZkpProof entity with TypeORM decorators (#340)

backend/src/modules/zkp/entities/proof.entity.ts

@@ -0,0 +1,94 @@
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  Column,
+  CreateDateColumn,
+  UpdateDateColumn,
+  Index,
+  Check,
+} from 'typeorm';
+
+export enum ProofStatus {
+  PENDING = 'pending',
+  VALID = 'valid',
+  INVALID = 'invalid',
+  EXPIRED = 'expired',
+  REVOKED = 'revoked',
+}
+
+/**
+ * Stores zero-knowledge proofs generated for pet vaccination records.
+ *
+ * Only public inputs are persisted; the private witness never leaves the
+ * ZkpService and is never stored in the database.
+ */
+@Entity('zkp_proofs')
+@Index('idx_zkp_proofs_pet_id', ['petId'])
+@Index('idx_zkp_proofs_vaccination_id', ['vaccinationId'])
+@Index('idx_zkp_proofs_status', ['status'])
+@Index('idx_zkp_proofs_expires_at', ['expiresAt'])
+@Check(`"expires_at" IS NULL OR "expires_at" > "created_at"`)
+export class ZkpProof {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  /** FK to the vaccination record this proof attests to. */
+  @Column({ name: 'vaccination_id' })
+  vaccinationId: string;
+
+  /** FK to the pet that owns the vaccination record. */
+  @Column({ name: 'pet_id' })
+  petId: string;
+
+  /**
+   * Non-sensitive public inputs exposed to verifiers.
+   * Contains fields such as petId, vaccineName, isValid, expiresAfter.
+   */
+  @Column({ type: 'jsonb', name: 'public_inputs' })
+  publicInputs: Record<string, unknown>;
+
+  /**
+   * Cryptographic proof string.
+   * In production: Groth16 π_A, π_B, π_C encoded as hex/base64.
+   * In simulation: SHA-256(publicInputs + commitment).
+   */
+  @Column({ type: 'text' })
+  proof: string;
+
+  /**
+   * HMAC-SHA256 commitment to the private witness.
+   * Allows re-verification without storing the witness itself.
+   */
+  @Column({ type: 'text' })
+  commitment: string;
+
+  /** Current lifecycle status of the proof. */
+  @Column({
+    type: 'enum',
+    enum: ProofStatus,
+    default: ProofStatus.PENDING,
+  })
+  status: ProofStatus;
+
+  /** Convenience flag; kept in sync with status for fast boolean queries. */
+  @Column({ default: true, name: 'is_valid' })
+  isValid: boolean;
+
+  /** Proof expires at this timestamp; null means no expiry. */
+  @Column({ type: 'timestamptz', nullable: true, name: 'expires_at' })
+  expiresAt: Date | null;
+
+  /** Timestamp of the most recent verification attempt. */
+  @Column({ type: 'timestamptz', nullable: true, name: 'verified_at' })
+  verifiedAt: Date | null;
+
+  /** Timestamp when the proof was revoked, if applicable. */
+  @Column({ type: 'timestamptz', nullable: true, name: 'revoked_at' })
+  revokedAt: Date | null;
+
+  @CreateDateColumn({ name: 'created_at' })
+  createdAt: Date;
+
+  @UpdateDateColumn({ name: 'updated_at' })
+  updatedAt: Date;
+}