feat: Add batch operations, dashboard redesign, hierarchical locations

## Batch Operations (#13)
- Add POST /spool/bulk/archive, /bulk/delete, /bulk/update endpoints
- Add row selection with checkboxes to spool list
- Add floating BatchActionBar with archive/unarchive/delete/move actions
- Add confirmation modals for all batch operations

## Dashboard Redesign (#12)
- Install recharts for pie charts
- Add AlertCards (low stock, pending jobs, needs weighing)
- Add MaterialDistributionChart (pie chart by material)
- Add QuickStats row (total spools, filaments, vendors, weight)
- Refactor home page layout with new components

## Hierarchical Locations (#9)
- Add Location model with self-referential parent relationship
- Add migration for location table and spool.location_id FK
- Add location database operations (CRUD, tree, full path)
- Add location API endpoints (list, tree, CRUD)
- Add LocationTreeSelect component with nested tree display
- Add LocationCreateModal for inline location creation
- Keep legacy location string field for backward compatibility

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

spoolman/database/models.py

@@ -12,6 +12,30 @@ class Base(AsyncAttrs, DeclarativeBase):
     pass
 
 
+class Location(Base):
+    """Hierarchical storage location (room, shelf, bin, etc.)."""
+
+    __tablename__ = "location"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    name: Mapped[str] = mapped_column(String(64))
+    parent_id: Mapped[Optional[int]] = mapped_column(ForeignKey("location.id", ondelete="SET NULL"), index=True)
+    location_type: Mapped[Optional[str]] = mapped_column(String(32), comment="Type: room, shelf, bin, etc.")
+    description: Mapped[Optional[str]] = mapped_column(String(256))
+
+    # Self-referential relationships
+    parent: Mapped[Optional["Location"]] = relationship(
+        "Location",
+        remote_side="Location.id",
+        back_populates="children",
+    )
+    children: Mapped[list["Location"]] = relationship(
+        "Location",
+        back_populates="parent",
+    )
+    spools: Mapped[list["Spool"]] = relationship(back_populates="location_obj")
+
+
 class Vendor(Base):
     __tablename__ = "vendor"
 
@@ -76,7 +100,13 @@ class Spool(Base):
     initial_weight: Mapped[Optional[float]] = mapped_column()
     spool_weight: Mapped[Optional[float]] = mapped_column()
     used_weight: Mapped[float] = mapped_column()
-    location: Mapped[Optional[str]] = mapped_column(String(64))
+    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"),
+        index=True,
+        comment="FK to hierarchical location.",
+    )
+    location_obj: Mapped[Optional["Location"]] = relationship(back_populates="spools")
     lot_nr: Mapped[Optional[str]] = mapped_column(String(64))
     comment: Mapped[Optional[str]] = mapped_column(String(1024))
     archived: Mapped[Optional[bool]] = mapped_column()