Add type hints to public APIs and configure mypy

- Improve mypy configuration with appropriate strictness settings
- Add comprehensive type hints to public API functions:
  - hookspecs.py: Type register_commands and prepare_connection hooks
  - plugins.py: Type get_plugins function and PluginManager
  - recipes.py: Type parsedate, parsedatetime, jsonsplit functions
  - utils.py: Type all public utility functions including rows_from_file,
    TypeTracker, ValueTracker, chunks, hash_record, flatten, etc.
  - db.py: Type Database, Queryable, Table, and View class methods
    including constructor, execute, query, table operations, etc.
- Exclude cli.py from strict checking (internal implementation detail)
- All public API modules now pass mypy type checking

sqlite_utils/recipes.py

@@ -1,11 +1,18 @@
+from typing import Any, Callable, Optional
+
 from dateutil import parser
 import json
 
-IGNORE = object()
-SET_NULL = object()
+IGNORE: object = object()
+SET_NULL: object = object()
 
 
-def parsedate(value, dayfirst=False, yearfirst=False, errors=None):
+def parsedate(
+    value: Optional[str],
+    dayfirst: bool = False,
+    yearfirst: bool = False,
+    errors: Optional[object] = None,
+) -> Optional[str]:
     """
     Parse a date and convert it to ISO date format: yyyy-mm-dd
     \b
@@ -31,7 +38,12 @@ def parsedate(value, dayfirst=False, yearfirst=False, errors=None):
             raise
 
 
-def parsedatetime(value, dayfirst=False, yearfirst=False, errors=None):
+def parsedatetime(
+    value: Optional[str],
+    dayfirst: bool = False,
+    yearfirst: bool = False,
+    errors: Optional[object] = None,
+) -> Optional[str]:
     """
     Parse a datetime and convert it to ISO datetime format: yyyy-mm-ddTHH:MM:SS
     \b
@@ -53,7 +65,9 @@ def parsedatetime(value, dayfirst=False, yearfirst=False, errors=None):
             raise
 
 
-def jsonsplit(value, delimiter=",", type=str):
+def jsonsplit(
+    value: str, delimiter: str = ",", type: Callable[[str], Any] = str
+) -> str:
     """
     Convert a string like a,b,c into a JSON array ["a", "b", "c"]
     """