chore: bump minimum Python from 3.8 to 3.9 (#336)

* chore: bump minimum Python from 3.8 to 3.9 and adopt PEP 585 builtins

- Update requires-python, classifiers, mypy target, and black target in pyproject.toml
- Replace Python 3.8 with 3.9 in CI matrix and nightly workflow
- Replace typing.List/Dict/Tuple/Set with builtin list/dict/tuple/set (PEP 585)
- Update all 3.8 version references in README, docs, website, and install.sh
- Fix test_wayland_no_tools to mock IBus availability
- Remove List from common_types re-exports and update test

* style: reformat test files for Black 26.x and pin version in CI

Black 26.x introduced parenthesized context manager formatting.
Reformat 7 test files and pin Black>=26,<27 in CI to prevent
future drift from unpinned version upgrades.

src/vocalinux/speech_recognition/command_processor.py

@@ -7,7 +7,6 @@ This module processes text commands from speech recognition, such as
 
 import logging
 import re
-from typing import List, Tuple
 
 logger = logging.getLogger(__name__)
 
@@ -99,7 +98,7 @@ class CommandProcessor:
         )
         self.format_cmd_regex = re.compile(format_cmd_pattern, re.IGNORECASE)
 
-    def process_text(self, text: str) -> Tuple[str, List[str]]:
+    def process_text(self, text: str) -> tuple[str, list[str]]:
         """
         Process text commands in the recognized text.