feat(ux): Sticky Save/Cancel buttons on forms (#38)

- Add sticky positioning to form action buttons (always visible at bottom)
- Add Ctrl+S / Cmd+S keyboard shortcut to save forms
- Create reusable useFormShortcuts hook
- Apply to all create forms: spool, filament, vendor

Fixes: https://github.com/Donkie/Spoolman/issues/274

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

client/src/pages/spools/create.tsx

@@ -5,7 +5,7 @@ import { Alert, Button, DatePicker, Divider, Form, Input, InputNumber, Radio, Se
 import TextArea from "antd/es/input/TextArea";
 import dayjs from "dayjs";
 import utc from "dayjs/plugin/utc";
-import { useEffect, useMemo, useState } from "react";
+import { useCallback, useEffect, useMemo, useState } from "react";
 import { ExtraFieldFormItem, ParsedExtras, StringifiedExtras } from "../../components/extraFields";
 import { FilamentCreateModal } from "../../components/filamentCreateModal";
 import { useSpoolmanLocations } from "../../components/otherModels";
@@ -14,6 +14,7 @@ import "../../utils/overrides.css";
 import { formatNumberOnUserInput, numberParser, numberParserAllowEmpty } from "../../utils/parsing";
 import { EntityType, useGetFields } from "../../utils/queryFields";
 import { getCurrencySymbol, useCurrency } from "../../utils/settings";
+import { useFormShortcuts } from "../../utils/useFormShortcuts";
 import { createFilamentFromExternal } from "../filaments/functions";
 import { IFilament } from "../filaments/model";
 import { useGetFilamentSelectOptions } from "./functions";
@@ -140,6 +141,12 @@ export const SpoolCreate: React.FC<IResourceComponentsProps & CreateOrCloneProps
     redirect(redirectTo);
   };
 
+  // Keyboard shortcut: Ctrl+S / Cmd+S to save
+  const handleSaveShortcut = useCallback(() => {
+    handleSubmit("list");
+  }, []);
+  useFormShortcuts(handleSaveShortcut);
+
   // Use useEffect to update the form's initialValues when the extra fields are loaded
   // This is necessary because the form is rendered before the extra fields are loaded
   useEffect(() => {