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/commands/datasheet_manager.py

@@ -12,7 +12,7 @@ No API key required.
 import logging
 import re
 from pathlib import Path
-from typing import Dict, List, Optional
+from typing import Dict, List, Optional, Tuple
 
 logger = logging.getLogger("kicad_interface")
 
@@ -49,7 +49,7 @@ class DatasheetManager:
         return None
 
     @staticmethod
-    def _find_lib_symbols_range(lines: List[str]):
+    def _find_lib_symbols_range(lines: List[str]) -> Tuple[Optional[int], Optional[int]]:
         """
         Find the line range of the (lib_symbols ...) section.
         Returns (start, end) line indices or (None, None) if not found.