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/structures/base.rs

@@ -1,34 +1,50 @@
+use crate::app::states::{Players, skirmish_states::structures::Structure};
 use ratatui::style::Color;
 
-use crate::app::states::Players;
-
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct BaseBuilding {
+    durability: u16,
+    stress: u8,
     owner: Players,
     level: u8,
 }
 
 impl BaseBuilding {
     pub fn new(owner: Players) -> Self {
-        Self { owner, level: b'1' }
-    }
-
-    pub fn get_tag(&self) -> char {
-        'B'
-    }
-
-    pub fn get_color(&self) -> Color {
-        match self.owner {
-            Players::Player => Color::LightBlue,
-            Players::Enemy => Color::LightRed,
+        Self {
+            durability: 1500,
+            stress: 0,
+            owner,
+            level: b'1',
         }
     }
 
     pub fn get_owner(&self) -> Players {
         self.owner
     }
+}
 
-    pub fn get_level(&self) -> char {
+impl Structure for BaseBuilding {
+    fn get_tag(&self) -> char {
+        'B'
+    }
+
+    fn get_color(&self) -> Color {
+        match self.owner {
+            Players::Player => Color::LightBlue,
+            Players::Enemy => Color::LightRed,
+        }
+    }
+
+    fn get_level(&self) -> char {
         self.level as char
     }
+
+    fn get_durability(&self) -> u16 {
+        self.durability
+    }
+
+    fn get_stress(&self) -> u8 {
+        self.stress
+    }
 }