fix: prevent NaN in health indicator calculations (#19378)

## Summary

Fixes #19377

- **Redis health**: The hit rate calculation divides by zero when both
`keyspace_hits` and `keyspace_misses` are `"0"` (common on fresh
instances). The string `"0"` is truthy so the guard
`statsData.keyspace_hits ? ...` doesn't catch this case, resulting in
`0/0 = NaN`. Fixed by computing the total first and checking it's a
valid non-zero number.
- **Database health**: The cache hit ratio query returns `null` when
`pg_statio_user_tables` is empty (no user tables). `parseFloat(null)` →
`NaN`. Fixed by adding a null check.

## Test plan

- [ ] Verify health indicators display correctly on a fresh instance
with no Redis keyspace activity
- [ ] Verify health indicators display correctly on a database with no
user tables
- [ ] Existing tests in `redis.health.spec.ts` still pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: easonysliu <easonysliu@tencent.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-server/src/engine/core-modules/admin-panel/indicators/database.health.ts

@@ -6,6 +6,7 @@ import {
 import { InjectDataSource } from '@nestjs/typeorm';
 
 import { DataSource } from 'typeorm';
+import { isDefined } from 'twenty-shared/utils';
 
 import { HEALTH_ERROR_MESSAGES } from 'src/engine/core-modules/admin-panel/constants/health-error-messages.constants';
 import { withHealthCheckTimeout } from 'src/engine/core-modules/admin-panel/utils/health-check-timeout.util';
@@ -89,7 +90,9 @@ export class DatabaseHealthIndicator {
         },
         databaseSize: databaseSize.size,
         performance: {
-          cacheHitRatio: Math.round(parseFloat(cacheHitRatio.ratio)) + '%',
+          cacheHitRatio: isDefined(cacheHitRatio.ratio)
+            ? Math.round(parseFloat(cacheHitRatio.ratio)) + '%'
+            : 'N/A',
           deadlocks: parseInt(deadlocks.deadlocks),
           slowQueries: parseInt(slowQueries.count),
         },

packages/twenty-server/src/engine/core-modules/admin-panel/indicators/redis.health.ts

@@ -4,6 +4,8 @@ import {
   HealthIndicatorService,
 } from '@nestjs/terminus';
 
+import { isDefined } from 'twenty-shared/utils';
+
 import { HEALTH_ERROR_MESSAGES } from 'src/engine/core-modules/admin-panel/constants/health-error-messages.constants';
 import { withHealthCheckTimeout } from 'src/engine/core-modules/admin-panel/utils/health-check-timeout.util';
 import { HealthStateManager } from 'src/engine/core-modules/admin-panel/utils/health-state-manager.util';
@@ -70,14 +72,19 @@ export class RedisHealthIndicator {
         },
         performance: {
           opsPerSecond: parseInt(statsData.instantaneous_ops_per_sec),
-          hitRate: statsData.keyspace_hits
-            ? Math.round(
-                (parseInt(statsData.keyspace_hits) /
-                  (parseInt(statsData.keyspace_hits) +
-                    parseInt(statsData.keyspace_misses))) *
-                  100,
-              ) + '%'
-            : '0%',
+          hitRate:
+            isDefined(statsData.keyspace_hits) &&
+            isDefined(statsData.keyspace_misses)
+              ? (() => {
+                  const hits = parseInt(statsData.keyspace_hits);
+                  const misses = parseInt(statsData.keyspace_misses);
+                  const total = hits + misses;
+
+                  return total > 0
+                    ? Math.round((hits / total) * 100) + '%'
+                    : '0%';
+                })()
+              : '0%',
           evictedKeys: parseInt(statsData.evicted_keys),
           expiredKeys: parseInt(statsData.expired_keys),
         },