style: Fix all mypy errors and add type hints to untyped function bodies

**Resolved all 65 mypy errors across 14 files and added type annotations to all previously untyped function bodies. Final result: 0 errors with --check-untyped-defs enabled, all 454 tests pass.**

`scrapling/core/_types.py`

  - Removed broken Self = object fallback — now requires typing_extensions for Python < 3.11

`scrapling/core/storage.py`

  - Fixed str/bytes mismatch in _get_hash() — used separate _identifier_bytes variable instead of reassigning from str to bytes

`scrapling/core/custom_types.py`

  - split() return type: Union[List, "TextHandlers"] → list[Any] (avoids LSP violation with parent list[str])
  - format() kwargs: **kwargs: str → **kwargs: object (matches parent str.format signature)
  - AttributesHandler.__init__: Added mapping: Any = None, **kwargs: Any and -> None
  - json_string property: Added -> bytes return type

`scrapling/core/mixins.py`

  - Changed self: "Selector" to self: Any on all mixin methods (mypy can't handle forward-reference self types on non-subclass mixins)
  - Added Dict[str, int] annotation for counter variable
  - Removed unused TYPE_CHECKING / Selector imports

`scrapling/parser.py (~30 errors)`

  - Added body: str | bytes pre-annotation for dual-type if/elif assignment
  - Used Dict[str, Any] kwargs dict for HTMLParser(...) to bypass incomplete lxml stubs missing default_doctype
  - Changed base_url=url or None → base_url=url or "" (avoids str | None vs str | bytes)
  - bool(adaptive) to guarantee bool type for __adaptive_enabled
  - Declared __text: Optional[TextHandler], __tag: Optional[str], __attributes: Optional[AttributesHandler] at top of __init__
  - cast(List, ...) for all XPath() call results (_find_all_elements, _find_all_elements_with_spaces)
  - Added Dict[float, List[Any]] for score_table, Dict[str, Any] for attributes
  - Changed score, checks = 0, 0 → score: float = 0; checks: int = 0 (two locations)
  - Renamed target → target_element in save() to avoid variable redefinition with different types
  - Wrapped node_text.clean() / .lower() in TextHandler(...) to preserve type

`scrapling/engines/_browsers/_page.py`

  - Added PageInfo[SyncPage] | PageInfo[AsyncPage] union type annotation to page_info variable

`scrapling/engines/_browsers/_validators.py`

  - Convert method_kwargs (TypedDict) to plain Dict[str, Any] before dynamic key access

`scrapling/engines/_browsers/_base.py`

  - Added _config declaration to BaseSessionMixin
  - Used cast(StealthConfig, self._config) in __generate_stealth_options to access stealth-only attributes
  - Added Tuple[str, ...] annotation for flags
  - Removed redundant narrower StealthConfig type annotation on self._config in StealthySessionMixin.__validate__
  - Widened SyncSession and AsyncSession fields (playwright, context, browser) to Any to support both playwright and patchright types
  - Added -> None to both start() methods

`scrapling/engines/_browsers/_stealth.py`

  - Added Optional, ProxyType imports
  - Annotated proxy: Optional[ProxyType] in both sync/async fetch loops
  - Annotated outer_box: Any at first declaration, removed duplicate type annotations in subsequent branches
  - Added -> None to sync and async start()
  - Added config: Any parameter type to _initialize_context
  - Removed redundant self.context: AsyncBrowserContext re-annotations in conditional branches

`scrapling/engines/_browsers/_controllers.py`

  - Added Optional, ProxyType imports
  - Annotated proxy: Optional[ProxyType] in both sync/async fetch loops
  - Added -> None to async start()
  - Removed redundant self.context: AsyncBrowserContext re-annotations

`scrapling/spiders/request.py`

  - Added Optional import, typed _fp: Optional[bytes] = None
  - Removed redundant body: bytes re-annotation

`scrapling/spiders/session.py`

  - Used separate client variable instead of reassigning session = session._client (avoids type incompatibility and fixes a bug where session._make_request was called instead of client._make_request)
  - Added -> None to SessionManager.__init__

`scrapling/engines/toolbelt/convertor.py`

  - Added list[Response] annotation for history in both sync/async methods

`scrapling/engines/static.py`

  - FetcherClient.__init__ and AsyncFetcherClient.__init__: Added **kwargs: Any and -> None

`scrapling/core/shell.py`

  - Wrapped re_sub(...) result in TextHandler(...) to maintain correct type
  - Added -> None to CurlParser.__init__
  - Added full type signature to create_wrapper, replaced wrapper.__signature__ = ... with setattr(wrapper, "__signature__", ...) to satisfy mypy
  - Added Callable to imports

scrapling/core/mixins.py

@@ -1,7 +1,4 @@
-from scrapling.core._types import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from scrapling.parser import Selector
+from scrapling.core._types import Any, Dict
 
 
 class SelectorsGeneration:
@@ -11,7 +8,11 @@ class SelectorsGeneration:
     Inspiration: https://searchfox.org/mozilla-central/source/devtools/shared/inspector/css-logic.js#591
     """
 
-    def _general_selection(self: "Selector", selection: str = "css", full_path: bool = False) -> str:  # type: ignore[name-defined]
+    # Note: This is a mixin class meant to be used with Selector.
+    # The methods access Selector attributes (._root, .parent, .attrib, .tag, etc.)
+    # through self, which will be a Selector instance at runtime.
+
+    def _general_selection(self: Any, selection: str = "css", full_path: bool = False) -> str:
         """Generate a selector for the current element.
         :return: A string of the generated selector.
         """
@@ -36,7 +37,7 @@ class SelectorsGeneration:
                     # if classes and css:
                     #     part += f".{'.'.join(classes)}"
                     # else:
-                    counter = {}
+                    counter: Dict[str, int] = {}
                     for child in target.parent.children:
                         counter.setdefault(child.tag, 0)
                         counter[child.tag] += 1
@@ -56,28 +57,28 @@ class SelectorsGeneration:
         return " > ".join(reversed(selectorPath)) if css else "//" + "/".join(reversed(selectorPath))
 
     @property
-    def generate_css_selector(self: "Selector") -> str:  # type: ignore[name-defined]
+    def generate_css_selector(self: Any) -> str:
         """Generate a CSS selector for the current element
         :return: A string of the generated selector.
         """
         return self._general_selection()
 
     @property
-    def generate_full_css_selector(self: "Selector") -> str:  # type: ignore[name-defined]
+    def generate_full_css_selector(self: Any) -> str:
         """Generate a complete CSS selector for the current element
         :return: A string of the generated selector.
         """
         return self._general_selection(full_path=True)
 
     @property
-    def generate_xpath_selector(self: "Selector") -> str:  # type: ignore[name-defined]
+    def generate_xpath_selector(self: Any) -> str:
         """Generate an XPath selector for the current element
         :return: A string of the generated selector.
         """
         return self._general_selection("xpath")
 
     @property
-    def generate_full_xpath_selector(self: "Selector") -> str:  # type: ignore[name-defined]
+    def generate_full_xpath_selector(self: Any) -> str:
         """Generate a complete XPath selector for the current element
         :return: A string of the generated selector.
         """