feat: Add configurable max_request_line_size to handle long URLs

This commit adds a new configuration option `max_request_line_size` that allows
users to increase the HTTP request line size limit. This is particularly useful
for handling very long continuation tokens that can cause 414 (URI Too Long) errors.

Changes:
- Add `max_request_line_size` property to Config class
- Configure Kemal server to use the custom limit if specified
- Document the option in config.example.yml with recommendations
- Add examples in docker-compose.yml for both YAML and env var configuration

The default behavior remains unchanged (8KB limit) unless explicitly configured.
This provides a solution for users experiencing 414 errors without affecting
existing installations.

src/invidious.cr

@@ -252,6 +252,11 @@ Kemal.config.app_name = "Invidious"
 {% end %}
 
 Kemal.run do |config|
+  # Set max request line size if configured
+  if max_size = CONFIG.max_request_line_size
+    config.server.not_nil!.max_request_line_size = max_size
+  end
+  
   if socket_binding = CONFIG.socket_binding
     File.delete?(socket_binding.path)
     # Create a socket and set its desired permissions

src/invidious/config.cr

@@ -157,6 +157,8 @@ class Config
   property host_binding : String = "0.0.0.0"
   # Path and permissions to make Invidious listen on a UNIX socket instead of a TCP port
   property socket_binding : SocketBindingConfig? = nil
+  # Maximum size of request line (in bytes), increase if you get 414 errors with long URLs
+  property max_request_line_size : Int32? = nil
   # Pool size for HTTP requests to youtube.com and ytimg.com (each domain has a separate pool of `pool_size`)
   property pool_size : Int32 = 100
   # HTTP Proxy configuration