feat: Add extra weight, price tracking, print history, usage analytics

- Extra Weight Field (#14): Track DryPods, custom holders in spool weight
  calculations. New extra_weight field on spool with DB migration.

- Price/Cost Tracking: Compute remaining_value based on remaining weight
  and price. Added column to spool list, inventory value on dashboard.

- Print History: Show print job history on spool detail page with
  collapsible table showing filename, filament used, status, dates.

- Usage Analytics: New dashboard component with time-series chart
  showing daily consumption, period selector (7/30/90 days), and
  material breakdown. New API endpoints for analytics data.

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

spoolman/api/v1/models.py

@@ -311,6 +311,12 @@ class Spool(BaseModel):
         description=("Weight of an empty spool (tare weight)."),
         examples=[246],
     )
+    extra_weight: Optional[float] = Field(
+        default=None,
+        ge=0,
+        description=("Extra weight to account for, such as DryPods, custom spool holders, etc."),
+        examples=[50],
+    )
     used_weight: float = Field(
         ge=0,
         description="Consumed weight of filament from the spool in grams.",
@@ -325,6 +331,12 @@ class Spool(BaseModel):
         ),
         examples=[5612.4],
     )
+    remaining_value: Optional[float] = Field(
+        default=None,
+        ge=0,
+        description="Estimated remaining value of filament on the spool based on remaining weight and price.",
+        examples=[12.50],
+    )
     used_length: float = Field(
         ge=0,
         description="Consumed length of filament from the spool in millimeters.",
@@ -389,6 +401,13 @@ class Spool(BaseModel):
             diameter=filament.diameter,
         )
 
+        # Calculate remaining value based on remaining weight and price
+        remaining_value: Optional[float] = None
+        price = item.price if item.price is not None else filament.price
+        initial_weight = item.initial_weight if item.initial_weight is not None else filament.weight
+        if remaining_weight is not None and price is not None and initial_weight is not None and initial_weight > 0:
+            remaining_value = round((remaining_weight / initial_weight) * price, 2)
+
         return Spool(
             id=item.id,
             registered=item.registered,
@@ -398,10 +417,12 @@ class Spool(BaseModel):
             price=item.price,
             initial_weight=item.initial_weight,
             spool_weight=item.spool_weight,
+            extra_weight=item.extra_weight,
             used_weight=item.used_weight,
             used_length=used_length,
             remaining_weight=remaining_weight,
             remaining_length=remaining_length,
+            remaining_value=remaining_value,
             location=item.location,
             lot_nr=item.lot_nr,
             comment=item.comment,