Backend: Upgrade all packages from "math/rand" to "math/rand/v2"

Signed-off-by: Michael Mayer <michael@photoprism.app>

AGENTS.md

@@ -194,6 +194,7 @@ Note: Across our public documentation, official images, and in production, the c
 
 - Go: run `make fmt-go swag-fmt` to reformat the backend code + Swagger annotations (see `Makefile` for additional targets)
   - Doc comments for packages and exported identifiers must be complete sentences that begin with the name of the thing being described and end with a period.
+  - All newly added functions, including unexported helpers, must have a concise doc comment that explains their behavior.
   - For short examples inside comments, indent code rather than using backticks; godoc treats indented blocks as preformatted.
 - Branding: Always spell the product name as `PhotoPrism`; this proper noun is an exception to generic naming rules.
 - Every Go package must contain a `<package>.go` file in its root (for example, `internal/auth/jwt/jwt.go`) with the standard license header and a short package description comment explaining its purpose.

internal/ai/tensorflow/util.go

@@ -1,12 +1,12 @@
 package tensorflow
 
-import "math/rand"
+import "math/rand/v2"
 
 func randomString(length int) string {
 	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
 	result := make([]byte, length)
 	for i := range result {
-		result[i] = charset[rand.Intn(len(charset))]
+		result[i] = charset[rand.IntN(len(charset))]
 	}
 	return string(result)
 }

internal/auth/jwt/verifier.go

@@ -7,7 +7,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"math/rand"
+	"math/rand/v2"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -49,7 +49,7 @@ const (
 )
 
 // randInt63n is defined for deterministic testing of jitter (overridable in tests).
-var randInt63n = rand.Int63n
+var randInt63n = rand.Int64N
 
 // cacheEntry stores the JWKS material cached on disk and in memory.
 type cacheEntry struct {

internal/config/config.go

@@ -25,8 +25,10 @@ Additional information can be found in our Developer Guide:
 package config
 
 import (
+	"context"
 	"crypto/tls"
 	"fmt"
+	"math/rand/v2"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -75,6 +77,8 @@ type Config struct {
 	db        *gorm.DB
 	dbVersion string
 	hub       *hub.Config
+	hubCancel context.CancelFunc
+	hubLock   sync.Mutex
 	token     string
 	serial    string
 	env       string
@@ -622,8 +626,22 @@ func (c *Config) SetLogLevel(level logrus.Level) {
 	SetLogLevel(level)
 }
 
+// stopHubTicker stops the periodic hub renewal ticker if it is running.
+func (c *Config) stopHubTicker() {
+	c.hubLock.Lock()
+	cancel := c.hubCancel
+	c.hubCancel = nil
+	c.hubLock.Unlock()
+
+	if cancel != nil {
+		cancel()
+	}
+}
+
 // Shutdown shuts down the active processes and closes the database connection.
 func (c *Config) Shutdown() {
+	c.stopHubTicker()
+
 	// App is no longer accepting requests.
 	c.ready.Store(false)
 
@@ -820,13 +838,24 @@ func (c *Config) initHub() {
 
 	c.hub.Propagate()
 
-	ticker := time.NewTicker(time.Hour * 24)
+	ctx, cancel := context.WithCancel(context.Background())
+
+	c.hubLock.Lock()
+	c.hubCancel = cancel
+	c.hubLock.Unlock()
+
+	d := 23*time.Hour + time.Duration(float64(2*time.Hour)*rand.Float64())
+	ticker := time.NewTicker(d)
 
 	go func() {
+		defer ticker.Stop()
+
 		for {
 			select {
 			case <-ticker.C:
 				c.RenewApiKeys()
+			case <-ctx.Done():
+				return
 			}
 		}
 	}()