refactor: phase 3 - API efficiency improvements

Add typed dataclasses for tuple returns:
- types.py: HeadlineItem, FetchResult, Block dataclasses with legacy tuple converters
- fetch.py: Add type hints and HeadlineTuple type alias

Add pyright for static type checking:
- Add pyright to dependencies
- Verify type coverage with pyright (0 errors in core modules)

This enables:
- Named types instead of raw tuples (better IDE support, self-documenting)
- Type-safe APIs across modules
- Backward compatibility via to_tuple/from_tuple methods

Note: Lazy imports skipped for render.py - startup impact is minimal.

pyproject.toml

@@ -22,6 +22,7 @@ classifiers = [
 dependencies = [
     "feedparser>=6.0.0",
     "Pillow>=10.0.0",
+    "pyright>=1.1.408",
 ]
 
 [project.optional-dependencies]