[Feature] Add a new feature that allow user to insert extra solid infills (#10611)

* refactor Infill rotation template

* clean up comments

* set default solid_infill_rotate_template to empty

* Fix an issue that infill_direction solid_infill_direction not working as expected

* Add Extra Solid Infill Feature
Introduced a new feature to insert extra solid infills at specific layers for enhanced strength in 3D prints.

* fix doc error

* fix image name

* support "#K" for Explicit Layer List

* update wiki

doc/print_settings/strength/strength_settings_infill.md

@@ -13,6 +13,7 @@ Infill is the internal structure of a 3D print, providing strength and support.
 - [Filter out tiny gaps](#filter-out-tiny-gaps)
 - [Anchor](#anchor)
 - [Internal Solid Infill](#internal-solid-infill)
+- [Extra Solid Infill](#extra-solid-infill)
 - [Sparse Infill Pattern](#sparse-infill-pattern)
 - [Credits](#credits)
 
@@ -153,11 +154,56 @@ OrcaSlicer tries to connect two close infill lines to a short perimeter segment.
 - **Anchor On**
 
 ![InfillAnchorOn](https://github.com/SoftFever/OrcaSlicer/blob/main/doc/images/fill/InfillAnchorOn.png?raw=true)
-
 ## Internal Solid Infill
 
 Line pattern of internal solid infill. If the [detect narrow internal solid infill](strength_settings_advanced#detect-narrow-internal-solid-infill) be enabled, the [concentric pattern](strength_settings_patterns#concentric) will be used for the small area.
 
+
+## Extra Solid Infill
+
+Insert extra solid infills at specific layers to add strength at critical points in your print. This feature allows you to strategically reinforce your part without changing the overall sparse infill density.
+
+![extra-solid-infill](https://github.com/SoftFever/OrcaSlicer/blob/main/doc/images/fill/extra-solid-infill.gif?raw=true)
+
+The pattern supports two formats:
+
+### Interval Pattern
+- **Simple interval**: `N` - Insert 1 solid layer every N layers, equal to `N#1`
+- **Multiple layers**: `N#K` - Insert K consecutive solid layers every N layers
+- **Optional K**: `N#` - Shorthand for `N#1`
+
+Examples:
+```
+5 or 5#1    # Insert 1 solid layer every 5 layers
+5#          # Same as 5#1
+10#2        # Insert 2 consecutive solid layers every 10 layers
+```
+
+### Explicit Layer List
+Specify exact layer numbers (1-based) using comma-separated values. Each entry may be a single layer `N` or a range `N#K` to insert K consecutive solid layers starting at layer N:
+
+```
+1,7,9       # Insert solid layers at layers 1, 7, and 9
+5,15,25     # Insert solid layers at layers 5, 15, and 25
+5,9#2,18    # Insert at 5; at 9 and 10 (because #2); and at 18
+```
+
+> [!NOTE]
+> - Layer numbers are 1-based (first layer is layer 1)
+> - `#K` is optional in both interval and explicit list entries (`N#` equals `N#1`)
+> - Solid layers are inserted in addition to the normal sparse infill pattern
+
+> [!TIP]
+> Use this feature to:
+> - Add strength at stress concentration points
+> - Reinforce mounting holes or attachment points
+> - Create internal structure for functional parts
+> - Add periodic reinforcement for tall prints
+> - Insert a single solid layer at a specific height by using an explicit list with a leading 0, which will be ignored because layer indices are 1-based. Example: `0,15` inserts a solid layer only at layer 15.
+
+> [!WARNING]
+> Layers that include solid infill can take significantly longer than surrounding layers. This time differential may lead to z-banding-like bulges. Consider adjusting cooling or speeds if you observe artifacts.
+
 ## Sparse Infill Pattern
 
 > [!TIP]