models: Restrict PdfSignaturePoint coordinates to float type

- Updated `_PdfSignaturePointModel` and `PdfSignaturePoint` to enforce
  `x` and `y` as `float` instead of accepting `str | int | float`.
- Ensures stricter type validation for signature positioning.

Assisted-by: Codex

Author: datalogics-kam

src/pdfrest/models/_internal.py

@@ -963,8 +963,8 @@ class PdfPresetRedactionModel(BaseModel):
 
 
 class _PdfSignaturePointModel(BaseModel):
-    x: str | int | float
-    y: str | int | float
+    x: float
+    y: float
 
 
 class _PdfSignatureLocationModel(BaseModel):

src/pdfrest/types/public.py

@@ -164,9 +164,10 @@ class PdfMergeSource(TypedDict, total=False):
 HtmlPageOrientation = Literal["portrait", "landscape"]
 HtmlWebLayout = Literal["desktop", "tablet", "mobile"]
 
+
 class PdfSignaturePoint(TypedDict):
-    x: str | int | float
-    y: str | int | float
+    x: float
+    y: float
 
 
 class PdfSignatureLocation(TypedDict):