Add base tags, adjust margins, update CLI defaults

Introduce `CellTag` and `Players` enums and extend `CellWidget` to carry
a tag.
Store player and enemy base coordinates in `BoardState` and tag those
cells.
Reduce horizontal margin from 3 to 1 in board layout helpers.
Change CLI defaults: map width default 42, map height min 11 and default
11.
Adjust offset calculation and render constraints to match the new
layout.

src/cli.rs

@@ -49,18 +49,18 @@ pub struct Cli {
         long,
         help = "Map width",
         value_name = "Positive integer [36; 108]",
-        default_value = "36",
+        default_value = "42",
         value_parser = value_parser!(u8).range(36..=108)
     )]
     pub map_width: u8,
 
-    /// Height of the generated map (13–50 tiles).
+    /// Height of the generated map (11–50 tiles).
     #[arg(
         long,
         help = "Map height",
-        value_name = "Positive integer [13; 39]",
-        default_value = "13",
-        value_parser = value_parser!(u8).range(13..=39)
+        value_name = "Positive integer [11; 39]",
+        default_value = "11",
+        value_parser = value_parser!(u8).range(11..=39)
     )]
     pub map_height: u8,