Fix implicit-nullable deprecation that 500'd every "not found" page

All twelve *NotFoundException classes declared their optional
$previous parameter as `\Throwable $previous = null` instead of
`?\Throwable $previous = null`. Implicitly marking a parameter
nullable this way has been deprecated since PHP 8.4, and production
(PHP 8.5) raises E_DEPRECATED the instant any of these constructors
runs - which is on every "not found" code path (Document, User,
Packet, Server, News Post/Category, Comment, Product, Event, User
Profile, and the Controller/Template lookup failures). Combined with
this app's error handler treating any raised error as fatal, that
meant e.g. GET /document/999999 500'd instead of rendering a 404.
Confirmed live before this fix: `curl -o /dev/null -w '%{http_code}'
https://bnetdocs.org/document/999999/x` returned 500.

Add tests/Exceptions/NotFoundExceptionsTest.php, which had no prior
coverage at all, asserting each class's constructor raises no PHP
error and still behaves correctly (throwable, preserves $previous).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: carlbennett

src/Exceptions/CommentNotFoundException.php

@@ -4,7 +4,7 @@
 
 class CommentNotFoundException extends DatabaseObjectNotFoundException
 {
-  public function __construct(\BNETDocs\Libraries\Comment|int $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\Comment|int $value, ?\Throwable $previous = null)
   {
     $v = is_int($value) ? $value : $value->getId();
     parent::__construct(\sprintf('Comment not found: %d', $v), 0, $previous);

src/Exceptions/ControllerNotFoundException.php

@@ -4,7 +4,7 @@
 
 class ControllerNotFoundException extends \InvalidArgumentException
 {
-  public function __construct(string $value, \Throwable $previous = null)
+  public function __construct(string $value, ?\Throwable $previous = null)
   {
     parent::__construct(\sprintf('Controller not found: %s', $value), 0, $previous);
   }

src/Exceptions/DocumentNotFoundException.php

@@ -4,7 +4,7 @@
 
 class DocumentNotFoundException extends DatabaseObjectNotFoundException
 {
-  public function __construct(\BNETDocs\Libraries\Document|int $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\Document|int $value, ?\Throwable $previous = null)
   {
     $v = is_int($value) ? $value : $value->getId();
     parent::__construct(\sprintf('Document not found: %d', $v), 0, $previous);

src/Exceptions/EventNotFoundException.php

@@ -4,7 +4,7 @@
 
 class EventNotFoundException extends DatabaseObjectNotFoundException
 {
-  public function __construct(\BNETDocs\Libraries\EventLog\Event|int $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\EventLog\Event|int $value, ?\Throwable $previous = null)
   {
     $v = is_int($value) ? $value : $value->getId();
     parent::__construct(\sprintf('Event log id not found: %d', $v), 0, $previous);

src/Exceptions/NewsCategoryNotFoundException.php

@@ -4,7 +4,7 @@
 
 class NewsCategoryNotFoundException extends DatabaseObjectNotFoundException
 {
-  public function __construct(\BNETDocs\Libraries\News\Category|int $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\News\Category|int $value, ?\Throwable $previous = null)
   {
     $v = is_int($value) ? $value : $value->getId();
     parent::__construct(\sprintf('News Category not found: %d', $v), 0, $previous);

src/Exceptions/NewsPostNotFoundException.php

@@ -4,7 +4,7 @@
 
 class NewsPostNotFoundException extends DatabaseObjectNotFoundException
 {
-  public function __construct(\BNETDocs\Libraries\News\Post|int $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\News\Post|int $value, ?\Throwable $previous = null)
   {
     $v = is_int($value) ? $value : $value->getId();
     parent::__construct(\sprintf('News Post not found: %d', $v), 0, $previous);

src/Exceptions/PacketNotFoundException.php

@@ -4,7 +4,7 @@
 
 class PacketNotFoundException extends DatabaseObjectNotFoundException
 {
-  public function __construct(\BNETDocs\Libraries\Packet\Packet|int $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\Packet\Packet|int $value, ?\Throwable $previous = null)
   {
     $v = is_int($value) ? $value : $value->getId();
     parent::__construct(\sprintf('Packet not found: %d', $v), 0, $previous);

src/Exceptions/ProductNotFoundException.php

@@ -4,7 +4,7 @@
 
 class ProductNotFoundException extends DatabaseObjectNotFoundException
 {
-  public function __construct(\BNETDocs\Libraries\Product|int $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\Product|int $value, ?\Throwable $previous = null)
   {
     $v = is_int($value) ? $value : $value->getBnetProductId();
     parent::__construct(\sprintf('Product not found: %d', $v), 0, $previous);

src/Exceptions/ServerNotFoundException.php

@@ -4,7 +4,7 @@
 
 class ServerNotFoundException extends DatabaseObjectNotFoundException
 {
-  public function __construct(\BNETDocs\Libraries\Server\Server|int $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\Server\Server|int $value, ?\Throwable $previous = null)
   {
     $v = is_int($value) ? $value : $value->getId();
     parent::__construct(\sprintf('Server not found: %d', $v), 0, $previous);

src/Exceptions/TemplateNotFoundException.php

@@ -4,7 +4,7 @@
 
 class TemplateNotFoundException extends \InvalidArgumentException
 {
-  public function __construct(\BNETDocs\Libraries\Core\Template|string $value, \Throwable $previous = null)
+  public function __construct(\BNETDocs\Libraries\Core\Template|string $value, ?\Throwable $previous = null)
   {
     $v = is_string($value) ? $value : $value->getTemplateFile();
     parent::__construct(\sprintf('Template not found: %s', $v), 0, $previous);