chore: enable strict mypy checks and fix pre-commit mypy hook

Add type annotations to all previously untyped functions and remove 9
suppressed error codes (call-arg, assignment, return-value, operator,
has-type, dict-item, misc, list-item, annotation-unchecked) by fixing
the underlying type issues.

Add [[tool.mypy.overrides]] with ignore_missing_imports for KiCAD-specific
modules (pcbnew, sexpdata, skip, cairosvg, kipy, PIL) so the pre-commit
mypy hook passes in its isolated venv. Add types-requests and pytest to
additional_dependencies in .pre-commit-config.yaml.

Also fixes several real bugs uncovered by stricter checks: incorrect static
calls to instance methods in swig_backend, wrong return type on get_size,
missing value param in BoardAPI.place_component, variable shadowing in
kicad_process.py, unqualified LibraryManager reference in kicad_interface,
and missing top-level Path import.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

python/utils/kicad_process.py

@@ -157,9 +157,9 @@ class KiCADProcessManager:
                 timeout=5 if system == "Windows" else None,
             )
             if result.returncode == 0:
-                path = result.stdout.strip().split("\n")[0]
-                logger.info(f"Found KiCAD executable: {path}")
-                return Path(path)
+                exe_path = result.stdout.strip().split("\n")[0]
+                logger.info(f"Found KiCAD executable: {exe_path}")
+                return Path(exe_path)
 
         # Platform-specific default paths
         if system == "Linux":