fix(api): resolve SQL unpacking crash and Event serialization errors

- Refactor SQL helpers in lib_sql_search to return empty tuples instead of False
- Add Pydantic pre-validators to Event_Base to coerce time objects to strings
- Improves API stability for Event searches and filtered lists

app/models/event_models.py

@@ -70,8 +70,8 @@ class Event_Base(BaseModel):
 
     recurring: Optional[bool]
     recurring_pattern: Optional[str]
-    recurring_start_time: Optional[datetime.time]
-    recurring_end_time: Optional[datetime.time]
+    recurring_start_time: Optional[str]
+    recurring_end_time: Optional[str]
     recurring_text: Optional[str]
 
     weekday_sunday: Optional[bool]
@@ -281,6 +281,12 @@ class Event_Base(BaseModel):
             return v.astimezone(pytz.UTC).isoformat()
         else: return v
 
+    @validator('recurring_start_time', 'recurring_end_time', pre=True, always=True)
+    def time_to_str(cls, v):
+        if isinstance(v, (datetime.time, datetime.timedelta)):
+            return str(v)
+        return v
+
     class Config:
         underscore_attrs_are_private = True
         allow_population_by_field_name = True
@@ -340,8 +346,8 @@ class Event_Meeting_Flat_Base(BaseModel):
 
     recurring: Optional[bool]
     recurring_pattern: Optional[str]
-    recurring_start_time: Optional[datetime.time]
-    recurring_end_time: Optional[datetime.time]
+    recurring_start_time: Optional[str]
+    recurring_end_time: Optional[str]
     recurring_text: Optional[str]
 
     weekday_sunday: Optional[bool]