feat: Add quick wins batch (#42, #43, #25, #35, #20, #36, #39)

- #42: Allow spools heavier than theoretical max (remove weight clamps)
- #43: Show filament custom fields on spool detail page
- #25: Sort spools by custom fields and remaining weight
- #35: Global search box for spool list
- #20: Gallery view for spools (color grid with progress bars)
- #36: Spool-level color override with ColorPicker
- #39: Cost analytics endpoint, total spent & avg cost/kg stats
- Fix: Filament select refresh after inline creation
- Fix: Parse temperatures from filament comments

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

spoolman/api/v1/other.py

@@ -291,3 +291,83 @@ async def get_usage_by_material(
     rows = result.all()
 
     return [MaterialUsage(material=row.material or "Unknown", weight_used=row.weight_used) for row in rows]
+
+
+class CostByMaterial(BaseModel):
+    """Cost breakdown by material."""
+
+    material: str = Field(description="Material name.")
+    total_cost: float = Field(description="Total cost spent on this material.")
+    total_weight: float = Field(description="Total initial weight purchased in grams.")
+
+
+class CostStats(BaseModel):
+    """Overall cost statistics."""
+
+    total_spent: float = Field(description="Sum of all spool purchase prices.")
+    total_weight_purchased: float = Field(description="Total initial weight of all spools in grams.")
+    avg_cost_per_kg: Optional[float] = Field(description="Average cost per kilogram of filament.")
+    cost_by_material: list[CostByMaterial] = Field(description="Cost breakdown by material type.")
+
+
+@router.get(
+    "/analytics/cost",
+    name="Get cost statistics",
+    description="Get overall cost tracking statistics across all spools.",
+    response_model=CostStats,
+)
+async def get_cost_stats(
+    *,
+    db: Annotated[AsyncSession, Depends(get_db_session)],
+) -> CostStats:
+    """Get cost statistics including total spent and cost per kg."""
+    # Use COALESCE(spool.price, filament.price) for effective price
+    effective_price = func.coalesce(models.Spool.price, models.Filament.price)
+    effective_weight = func.coalesce(models.Spool.initial_weight, models.Filament.weight)
+
+    # Total spent and total weight across all spools (including archived)
+    totals_stmt = (
+        sqlalchemy.select(
+            func.sum(effective_price).label("total_spent"),
+            func.sum(effective_weight).label("total_weight"),
+        )
+        .join(models.Filament, models.Spool.filament_id == models.Filament.id)
+        .where(effective_price.isnot(None))
+    )
+    totals_result = await db.execute(totals_stmt)
+    totals_row = totals_result.one()
+
+    total_spent = totals_row.total_spent or 0.0
+    total_weight_purchased = totals_row.total_weight or 0.0
+    avg_cost_per_kg = (total_spent / total_weight_purchased * 1000) if total_weight_purchased > 0 else None
+
+    # Cost by material
+    material_stmt = (
+        sqlalchemy.select(
+            func.coalesce(models.Filament.material, "Unknown").label("material"),
+            func.sum(effective_price).label("total_cost"),
+            func.sum(effective_weight).label("total_weight"),
+        )
+        .join(models.Filament, models.Spool.filament_id == models.Filament.id)
+        .where(effective_price.isnot(None))
+        .group_by(models.Filament.material)
+        .order_by(func.sum(effective_price).desc())
+    )
+    material_result = await db.execute(material_stmt)
+    material_rows = material_result.all()
+
+    cost_by_material = [
+        CostByMaterial(
+            material=row.material or "Unknown",
+            total_cost=row.total_cost or 0.0,
+            total_weight=row.total_weight or 0.0,
+        )
+        for row in material_rows
+    ]
+
+    return CostStats(
+        total_spent=total_spent,
+        total_weight_purchased=total_weight_purchased,
+        avg_cost_per_kg=avg_cost_per_kg,
+        cost_by_material=cost_by_material,
+    )