feat: Add temperature ranges for extruder and bed temps (#5)

Store extruder and bed temperatures as min/max ranges instead of
single values for more accurate filament specifications.

Backend changes:
- Add 4 new columns: settings_extruder_temp_min/max, settings_bed_temp_min/max
- Keep old columns for backward compatibility (marked deprecated)
- Alembic migration copies existing values to both min and max
- Update Pydantic models and API endpoints

Frontend changes:
- Filament model updated with new fields
- Create form uses min/max input pairs with Space.Compact
- Import from external DB populates both min and max with same value
- Label template updated to show ranges: "ET: 190-220 °C"
- Template help includes new tags

Labels now display temperature ranges like "190-220°C" which is more
useful for printing than a single recommended value.

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

spoolman/api/v1/filament.py

@@ -75,15 +75,39 @@ class FilamentParameters(BaseModel):
     settings_extruder_temp: Optional[int] = Field(
         None,
         ge=0,
-        description="Overridden extruder temperature, in °C.",
+        description="Overridden extruder temperature, in °C. Deprecated: use settings_extruder_temp_min/max.",
         examples=[210],
     )
     settings_bed_temp: Optional[int] = Field(
         None,
         ge=0,
-        description="Overridden bed temperature, in °C.",
+        description="Overridden bed temperature, in °C. Deprecated: use settings_bed_temp_min/max.",
         examples=[60],
     )
+    settings_extruder_temp_min: Optional[int] = Field(
+        None,
+        ge=0,
+        description="Minimum extruder temperature, in °C.",
+        examples=[190],
+    )
+    settings_extruder_temp_max: Optional[int] = Field(
+        None,
+        ge=0,
+        description="Maximum extruder temperature, in °C.",
+        examples=[220],
+    )
+    settings_bed_temp_min: Optional[int] = Field(
+        None,
+        ge=0,
+        description="Minimum bed temperature, in °C.",
+        examples=[50],
+    )
+    settings_bed_temp_max: Optional[int] = Field(
+        None,
+        ge=0,
+        description="Maximum bed temperature, in °C.",
+        examples=[70],
+    )
     color_hex: Optional[str] = Field(
         None,
         description=(
@@ -454,6 +478,10 @@ async def create(  # noqa: ANN201
         comment=body.comment,
         settings_extruder_temp=body.settings_extruder_temp,
         settings_bed_temp=body.settings_bed_temp,
+        settings_extruder_temp_min=body.settings_extruder_temp_min,
+        settings_extruder_temp_max=body.settings_extruder_temp_max,
+        settings_bed_temp_min=body.settings_bed_temp_min,
+        settings_bed_temp_max=body.settings_bed_temp_max,
         color_hex=body.color_hex,
         multi_color_hexes=body.multi_color_hexes,
         multi_color_direction=body.multi_color_direction,