Add last_update_date filtering and improve time interface DX

Part A: Add last_update_date filtering (client-side)
- Add updated_since parameter (accepts datetime object or ISO string)
- Add updated_in_past_hours parameter (accepts int or timedelta)
- Implement _apply_last_update_date_filter() method for client-side filtering
- Add mutual exclusion validation for updated_* parameters

Part B: Improve time interface DX
- Accept datetime/timedelta objects for datetime_from, datetime_to
- Accept timedelta objects for past_hours, past_days
- Add type conversion helper functions in utils.py
- Improve validation error messages with specific examples
- Update validate_datetime to accept datetime objects

Helper functions added:
- convert_to_datetime_string() - Converts datetime objects to ISO strings
- extract_timedelta_hours() - Extracts hours from timedelta objects
- extract_timedelta_days() - Extracts days from timedelta objects
- validate_last_update_filters() - Validates last_update_date parameters

All changes are backward compatible - existing string/int parameters still work.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

homeharvest/core/scrapers/__init__.py

@@ -33,6 +33,10 @@ class ScraperInput(BaseModel):
     datetime_from: str | None = None
     datetime_to: str | None = None
 
+    # New last_update_date filtering parameters
+    updated_since: str | None = None
+    updated_in_past_hours: int | None = None
+
     # New property filtering parameters
     beds_min: int | None = None
     beds_max: int | None = None
@@ -115,6 +119,10 @@ class Scraper:
         self.datetime_from = scraper_input.datetime_from
         self.datetime_to = scraper_input.datetime_to
 
+        # New last_update_date filtering
+        self.updated_since = scraper_input.updated_since
+        self.updated_in_past_hours = scraper_input.updated_in_past_hours
+
         # New property filtering
         self.beds_min = scraper_input.beds_min
         self.beds_max = scraper_input.beds_max