feat: Add inline creation modals for filament and vendor (#1)

When creating a spool, users can now create a new filament directly
from the filament dropdown without leaving the page. Similarly, when
creating a filament, users can create a new vendor inline.

New components:
- VendorCreateModal: Simple modal for quick vendor creation
- FilamentCreateModal: Modal with essential fields + nested vendor creation

Changes:
- Added dropdownRender to filament Select in spool create page
- Added dropdownRender to vendor Select in filament create page
- Added translation keys for success messages and placeholders
- Pre-fills sensible defaults (diameter 1.75mm, density 1.24 g/cm³)

Closes #1

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

client/public/locales/en/common.json

@@ -243,6 +243,7 @@
             "name": "Filament name, to distinguish this filament type among others from the same manufacturer. Should contain the color for example.",
             "material": "E.g. PLA, ABS, PETG, etc.",
             "price": "Price of a full spool.",
+            "density": "Auto-filled based on material. Standard: PLA 1.24, ABS 1.04, PETG 1.27 g/cm³.",
             "weight": "The filament weight of a full spool (net weight). This should not include the weight of the spool itself, only the filament. It is what is usually written on the packaging.",
             "spool_weight": "The weight of an empty spool. Used to determine measured weight of a spool.",
             "article_number": "E.g. EAN, UPC, etc.",
@@ -259,7 +260,10 @@
         "form": {
             "filament_updated": "This filament has been updated by someone/something else since you opened this page. Saving will overwrite those changes!",
             "import_external": "Import from External",
-            "import_external_description": "Select a filament in the list to automatically populate its details in the filament creation form. This will overwrite any data you have entered in the form.<br><br>A Manufacturer object will be created automatically when you click Ok, if necessary."
+            "import_external_description": "Select a filament in the list to automatically populate its details in the filament creation form. This will overwrite any data you have entered in the form.<br><br>A Manufacturer object will be created automatically when you click Ok, if necessary.",
+            "created_success": "Created filament \"{{name}}\"",
+            "vendor_placeholder": "Select a manufacturer",
+            "name_placeholder": "E.g. Matte Black"
         },
         "buttons": {
             "add_spool": "Add Spool"
@@ -287,7 +291,9 @@
             "show_title": "[Manufacturer #{{id}}] {{name}}"
         },
         "form": {
-            "vendor_updated": "This manufacturer has been updated by someone/something else since you opened this page. Saving will overwrite those changes!"
+            "vendor_updated": "This manufacturer has been updated by someone/something else since you opened this page. Saving will overwrite those changes!",
+            "created_success": "Created manufacturer \"{{name}}\"",
+            "name_required": "Name is required"
         }
     },
     "home": {