Refactor runner and installation scripts for improved functionality

- Removed the `--disable-hiprt` flag from the runner command, simplifying the rendering options for users.
- Updated the `jiggablend-runner` script and README to reflect the removal of the HIPRT control flag, enhancing clarity in usage instructions.
- Enhanced the installation script to provide clearer examples for running the jiggablend manager and runner, improving user experience during setup.
- Implemented a more robust GPU backend detection mechanism, allowing for better compatibility with various hardware configurations.

internal/config/config.go

@@ -21,8 +21,16 @@ const (
 	KeyFixedAPIKey          = "fixed_api_key"
 	KeyRegistrationEnabled  = "registration_enabled"
 	KeyProductionMode       = "production_mode"
-	KeyAllowedOrigins        = "allowed_origins"
+	KeyAllowedOrigins       = "allowed_origins"
 	KeyFramesPerRenderTask  = "frames_per_render_task"
+
+	// Operational limits (seconds / bytes / counts)
+	KeyRenderTimeoutSecs      = "render_timeout_seconds"
+	KeyEncodeTimeoutSecs      = "encode_timeout_seconds"
+	KeyMaxUploadBytes         = "max_upload_bytes"
+	KeySessionCookieMaxAge    = "session_cookie_max_age"
+	KeyAPIRateLimit           = "api_rate_limit"
+	KeyAuthRateLimit          = "auth_rate_limit"
 )
 
 // Config manages application configuration stored in the database
@@ -311,3 +319,34 @@ func (c *Config) GetFramesPerRenderTask() int {
 	return n
 }
 
+// RenderTimeoutSeconds returns the per-frame render timeout in seconds (default 3600 = 1 hour).
+func (c *Config) RenderTimeoutSeconds() int {
+	return c.GetIntWithDefault(KeyRenderTimeoutSecs, 3600)
+}
+
+// EncodeTimeoutSeconds returns the video encode timeout in seconds (default 86400 = 24 hours).
+func (c *Config) EncodeTimeoutSeconds() int {
+	return c.GetIntWithDefault(KeyEncodeTimeoutSecs, 86400)
+}
+
+// MaxUploadBytes returns the maximum upload size in bytes (default 50 GB).
+func (c *Config) MaxUploadBytes() int64 {
+	v := c.GetIntWithDefault(KeyMaxUploadBytes, 50<<30)
+	return int64(v)
+}
+
+// SessionCookieMaxAgeSec returns the session cookie max-age in seconds (default 86400 = 24 hours).
+func (c *Config) SessionCookieMaxAgeSec() int {
+	return c.GetIntWithDefault(KeySessionCookieMaxAge, 86400)
+}
+
+// APIRateLimitPerMinute returns the API rate limit (requests per minute per IP, default 100).
+func (c *Config) APIRateLimitPerMinute() int {
+	return c.GetIntWithDefault(KeyAPIRateLimit, 100)
+}
+
+// AuthRateLimitPerMinute returns the auth rate limit (requests per minute per IP, default 10).
+func (c *Config) AuthRateLimitPerMinute() int {
+	return c.GetIntWithDefault(KeyAuthRateLimit, 10)
+}
+