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>

client/src/pages/home/components/QuickStats.tsx

@@ -0,0 +1,100 @@
+import { HighlightOutlined, InboxOutlined, DatabaseOutlined, UserOutlined } from "@ant-design/icons";
+import { useList, useTranslate } from "@refinedev/core";
+import { Card, Col, Row, Statistic, theme } from "antd";
+import { useMemo } from "react";
+import { Link } from "react-router";
+import { IFilament } from "../../filaments/model";
+import { ISpool } from "../../spools/model";
+import { IVendor } from "../../vendors/model";
+
+const { useToken } = theme;
+
+export function QuickStats() {
+  const t = useTranslate();
+  const { token } = useToken();
+
+  const { result: filamentsResult, query: filamentsQuery } = useList<IFilament>({
+    resource: "filament",
+    pagination: { pageSize: 1 },
+  });
+
+  const { result: vendorsResult, query: vendorsQuery } = useList<IVendor>({
+    resource: "vendor",
+    pagination: { pageSize: 1 },
+  });
+
+  // Fetch all spools for total weight calculation
+  const { result: spoolsResult, query: spoolsQuery } = useList<ISpool>({
+    resource: "spool",
+    pagination: { pageSize: 1000 },
+    meta: {
+      queryParams: {
+        allow_archived: false,
+      },
+    },
+  });
+
+  // Calculate total remaining weight
+  const totalWeight = useMemo(() => {
+    const data = spoolsResult?.data || [];
+    return data.reduce((sum, spool) => sum + (spool.remaining_weight ?? 0), 0);
+  }, [spoolsResult?.data]);
+
+  const formatWeight = (grams: number) => {
+    if (grams >= 1000) {
+      return `${(grams / 1000).toFixed(1)} kg`;
+    }
+    return `${Math.round(grams)} g`;
+  };
+
+  return (
+    <Row gutter={[12, 12]} style={{ marginTop: 16 }}>
+      <Col xs={12} sm={6}>
+        <Link to="/spool">
+          <Card hoverable size="small">
+            <Statistic
+              title={t("home.quick_stats.total_spools")}
+              value={spoolsResult?.total ?? 0}
+              loading={spoolsQuery.isLoading}
+              prefix={<InboxOutlined />}
+            />
+          </Card>
+        </Link>
+      </Col>
+      <Col xs={12} sm={6}>
+        <Link to="/filament">
+          <Card hoverable size="small">
+            <Statistic
+              title={t("home.quick_stats.total_filaments")}
+              value={filamentsResult?.total ?? 0}
+              loading={filamentsQuery.isLoading}
+              prefix={<HighlightOutlined />}
+            />
+          </Card>
+        </Link>
+      </Col>
+      <Col xs={12} sm={6}>
+        <Link to="/vendor">
+          <Card hoverable size="small">
+            <Statistic
+              title={t("home.quick_stats.total_vendors")}
+              value={vendorsResult?.total ?? 0}
+              loading={vendorsQuery.isLoading}
+              prefix={<UserOutlined />}
+            />
+          </Card>
+        </Link>
+      </Col>
+      <Col xs={12} sm={6}>
+        <Card size="small">
+          <Statistic
+            title={t("home.quick_stats.total_weight")}
+            value={formatWeight(totalWeight)}
+            loading={spoolsQuery.isLoading}
+            prefix={<DatabaseOutlined />}
+          />
+        </Card>
+      </Col>
+    </Row>
+  );
+}