feat(backend): add password reset via email

- Add PasswordResetToken entity, repository (Flyway V8 migration)
- PasswordResetService: token generation, validation, nightly cleanup
- AuthController: POST /api/auth/forgot-password and /api/auth/reset-password (both permitAll)
- AuthE2EController (@Profile("e2e")): GET /api/auth/reset-token-for-test for CI testing
- spring-boot-starter-mail dependency; JavaMailSender optional (@Autowired required=false)
- mail health indicator disabled; mail config via MAIL_HOST/PORT/USERNAME/PASSWORD env vars
- 5 unit tests written TDD-style (all pass)

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

backend/src/main/resources/application.yaml

@@ -24,6 +24,23 @@ spring:
       max-file-size: 50MB
       max-request-size: 50MB
 
+  mail:
+    host: ${MAIL_HOST:}
+    port: ${MAIL_PORT:587}
+    username: ${MAIL_USERNAME:}
+    password: ${MAIL_PASSWORD:}
+    properties:
+      mail:
+        smtp:
+          auth: true
+          starttls:
+            enable: true
+
+management:
+  health:
+    mail:
+      enabled: false
+
 springdoc:
   api-docs:
     enabled: false
@@ -38,6 +55,11 @@ app:
     bucket: ${S3_BUCKET_NAME}
     region: ${S3_REGION}
 
+  base-url: ${APP_BASE_URL:http://localhost:3000}
+
+  mail:
+    from: ${APP_MAIL_FROM:noreply@familienarchiv.local}
+
   admin:
     username: ${APP_ADMIN_USERNAME:admin}
     password: ${APP_ADMIN_PASSWORD:admin123}

backend/src/main/resources/db/migration/V8__add_password_reset_tokens.sql

@@ -0,0 +1,10 @@
+CREATE TABLE password_reset_tokens (
+    id          UUID         PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id     UUID         NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    token       VARCHAR(64)  NOT NULL UNIQUE,
+    expires_at  TIMESTAMP    NOT NULL,
+    used        BOOLEAN      NOT NULL DEFAULT FALSE,
+    created_at  TIMESTAMP    NOT NULL DEFAULT now()
+);
+
+CREATE INDEX idx_prt_token ON password_reset_tokens(token);