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/database/models.py

@@ -104,6 +104,11 @@ class Spool(Base):
         default=None,
         comment="Extra weight to account for (DryPods, custom holders, etc.).",
     )
+    color_hex: Mapped[Optional[str]] = mapped_column(
+        String(8),
+        default=None,
+        comment="Spool-level color override (hex without #).",
+    )
     location: Mapped[Optional[str]] = mapped_column(String(64), comment="Legacy flat location string.")
     location_id: Mapped[Optional[int]] = mapped_column(
         ForeignKey("location.id", ondelete="SET NULL"),