Move ZoomLevel into skirmish_states

Introduce Structure and Unit traits with enum wrappers.
Replace old zoom helper with ZoomLevel methods.
Update imports, BoardState, CellWidget, and CLI to use new locations.

src/app/states/skirmish_states/units/miner.rs

@@ -1,4 +1,4 @@
-use crate::app::states::Players;
+use crate::app::states::{Players, skirmish_states::units::Unit};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct MinerUnit {
@@ -9,8 +9,14 @@ impl MinerUnit {
     pub fn new(owner: Players) -> Self {
         Self { owner }
     }
+}
 
-    pub fn get_tag(self) -> char {
+impl Unit for MinerUnit {
+    fn get_owner(&self) -> Players {
+        self.owner
+    }
+
+    fn get_tag(&self) -> char {
         'M'
     }
 }

src/app/states/skirmish_states/units/mod.rs

@@ -1,3 +1,7 @@
 mod miner;
+mod units_enum;
+mod units_trait;
 
 pub use miner::MinerUnit;
+pub use units_enum::Units;
+pub use units_trait::{OptionalUnit, Unit};

src/app/states/skirmish_states/units/units_enum.rs

@@ -0,0 +1,20 @@
+use crate::app::states::skirmish_states::units::{MinerUnit, OptionalUnit, Unit};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Units {
+    Miner(MinerUnit),
+}
+
+impl Units {
+    pub fn get_tag(&self) -> char {
+        match self {
+            Units::Miner(m) => m.get_tag(),
+        }
+    }
+}
+
+impl OptionalUnit for Option<Units> {
+    fn try_get_tag(&self) -> char {
+        self.map_or(' ', |u| u.get_tag())
+    }
+}

src/app/states/skirmish_states/units/units_trait.rs

@@ -0,0 +1,10 @@
+use crate::app::states::Players;
+
+pub trait Unit {
+    fn get_owner(&self) -> Players;
+    fn get_tag(&self) -> char;
+}
+
+pub trait OptionalUnit {
+    fn try_get_tag(&self) -> char;
+}