feat(monitoring): add Redis exporter + Sentry docs to deployment guide

- Add redis-exporter container to docker-compose (oliver006/redis_exporter, 32MB)
- Add Redis scrape target to Prometheus config
- Add 4 Redis alert rules: RedisDown, HighMemory, HighConnections, RejectedConnections
- Document Step 19b (Sentry Error Tracking) in Hetzner deployment guide
- Document Step 19c (Redis Monitoring) in Hetzner deployment guide
- Update resource budget and port reference tables

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

.idea/inspectionProfiles/Project_Default.xml

@@ -7,4 +7,4 @@
       </option>
     </inspection_tool>
   </profile>
-</component>
+</component>

.idea/inspectionProfiles/profiles_settings.xml

@@ -3,4 +3,4 @@
     <option name="USE_PROJECT_PROFILE" value="false" />
     <version value="1.0" />
   </settings>
-</component>
+</component>

.idea/modules.xml

@@ -5,4 +5,4 @@
       <module fileurl="file://$PROJECT_DIR$/.idea/fastapi-multitenant-ecommerce.iml" filepath="$PROJECT_DIR$/.idea/fastapi-multitenant-ecommerce.iml" />
     </modules>
   </component>
-</project>
+</project>