Add bottle size, bourbon list modal, and stat improvements

- Add bottle_size field to User model and UserResponse/UserUpdate schemas
- Settings modal includes bottle size input (shots capacity)
- Community bottles and My Bottle page show fill bar based on bottle size
- Community bottle cards are clickable — opens searchable bourbon list modal
- Add total_shots_added stat to replace duplicate net volume on dashboard
- Reorder dashboard stats: Bourbons Added, Total Poured In, Shots Remaining, Est. Proof
- Theme-matched custom scrollbar (amber on dark)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/schemas/entry.py

@@ -29,6 +29,7 @@ class EntryResponse(BaseModel):
 
 class BottleStats(BaseModel):
     total_add_entries: int
+    total_shots_added: float
     current_total_shots: float
     estimated_proof: Optional[float]
 
@@ -38,3 +39,5 @@ class PublicUserStats(BaseModel):
     total_add_entries: int
     current_total_shots: float
     estimated_proof: Optional[float]
+    bottle_size: Optional[float]
+    bourbons: list[str]