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>

migrations/versions/2025_01_22_0100-g7h8i9j0k1l2_add_spool_color_hex.py

@@ -0,0 +1,25 @@
+"""Add spool color_hex override.
+
+Revision ID: g7h8i9j0k1l2
+Revises: f6g7h8i9j0k1
+Create Date: 2025-01-22 01:00:00.000000
+
+"""
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision = "g7h8i9j0k1l2"
+down_revision = "f6g7h8i9j0k1"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    """Add color_hex column to spool table."""
+    op.add_column("spool", sa.Column("color_hex", sa.String(length=8), nullable=True))
+
+
+def downgrade() -> None:
+    """Remove color_hex column from spool table."""
+    op.drop_column("spool", "color_hex")