[fix](trx-core): expose rig min tuning step and align UI tuning

Add min_freq_step_hz to RigCapabilities, set backend values, and make HTTP frontend parse suffix-less frequency input using the selected unit while snapping set/jog frequencies to rig step granularity.

Co-authored-by: Codex <codex@openai.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

src/trx-core/src/rig/controller/handlers.rs

@@ -542,6 +542,7 @@ mod tests {
                     model: "Mock".to_string(),
                     revision: "1.0".to_string(),
                     capabilities: RigCapabilities {
+                        min_freq_step_hz: 1,
                         supported_bands: vec![],
                         supported_modes: vec![],
                         num_vfos: 2,
@@ -595,6 +596,7 @@ mod tests {
                     model: "Mock".to_string(),
                     revision: "1.0".to_string(),
                     capabilities: RigCapabilities {
+                        min_freq_step_hz: 1,
                         supported_bands: vec![],
                         supported_modes: vec![],
                         num_vfos: 2,

src/trx-core/src/rig/controller/machine.rs

@@ -439,6 +439,7 @@ mod tests {
             model: "Mock".to_string(),
             revision: "1.0".to_string(),
             capabilities: RigCapabilities {
+                min_freq_step_hz: 1,
                 supported_bands: vec![],
                 supported_modes: vec![],
                 num_vfos: 2,

src/trx-core/src/rig/mod.rs

@@ -39,6 +39,8 @@ pub struct RigInfo {
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct RigCapabilities {
+    #[serde(default = "default_min_freq_step_hz")]
+    pub min_freq_step_hz: u64,
     pub supported_bands: Vec<Band>,
     pub supported_modes: Vec<RigMode>,
     pub num_vfos: usize,
@@ -51,6 +53,10 @@ pub struct RigCapabilities {
     pub split: bool,
 }
 
+fn default_min_freq_step_hz() -> u64 {
+    1
+}
+
 /// Common interface for rig backends.
 pub trait Rig {
     fn info(&self) -> &RigInfo;