Fix refill-only colors to have 0 spools instead of 1

- Add migration to correct 14 colors that should be refill-only
- Create helper script for applying the fix
- Add frontend tracking for refill-only colors
- Update README with current project state
- Add development guidance documentation

database/migrations/015_fix_refill_only_colors.sql

@@ -0,0 +1,83 @@
+-- Migration: Fix refill-only colors to have 0 spools instead of 1
+-- These colors should only be available as refills, not as regular spools
+
+-- First, add Nardo Gray to colors table if it doesn't exist
+INSERT INTO colors (name, hex) VALUES 
+    ('Nardo Gray', '#747474')
+ON CONFLICT (name) DO NOTHING;
+
+-- Update all refill-only colors to have spulna = 0
+-- This ensures they can only be purchased as refills
+UPDATE filaments 
+SET 
+    spulna = 0,
+    kolicina = refill  -- Total quantity should equal refill count only
+WHERE tip = 'PLA' 
+AND finish = 'Basic'
+AND boja IN (
+    -- Colors specified by user as refill-only
+    'Nardo Gray',
+    'Blue Grey',     -- Note: Database uses "Blue Grey" not "Blue Gray"
+    'Light Gray',
+    'Brown',
+    'Beige',
+    'Bronze',
+    'Purple',
+    'Cobalt Blue',
+    'Turquoise',
+    'Bright Green',
+    'Yellow',
+    'Gold',
+    'Orange',
+    'Maroon Red'
+);
+
+-- Also handle any existing entries with alternate spellings
+UPDATE filaments 
+SET 
+    spulna = 0,
+    kolicina = refill
+WHERE tip = 'PLA' 
+AND finish = 'Basic'
+AND (
+    boja = 'Blue Gray'  -- Handle alternate spelling if it exists
+);
+
+-- Ensure these colors maintain their refill-only status
+-- even if they don't exist yet (for future inserts)
+INSERT INTO filaments (tip, finish, boja, boja_hex, refill, spulna, kolicina, cena)
+SELECT 
+    'PLA' as tip,
+    'Basic' as finish,
+    c.name as boja,
+    c.hex as boja_hex,
+    0 as refill,      -- Start with 0 refills
+    0 as spulna,      -- Always 0 spools for refill-only
+    0 as kolicina,    -- Total is 0
+    '3499' as cena    -- Refill price only
+FROM colors c
+WHERE c.name IN (
+    'Nardo Gray',
+    'Blue Grey',
+    'Light Gray', 
+    'Brown',
+    'Beige',
+    'Bronze',
+    'Purple',
+    'Cobalt Blue',
+    'Turquoise',
+    'Bright Green',
+    'Yellow',
+    'Gold',
+    'Orange',
+    'Maroon Red'
+)
+AND NOT EXISTS (
+    SELECT 1 FROM filaments f 
+    WHERE f.tip = 'PLA' 
+    AND f.finish = 'Basic' 
+    AND f.boja = c.name
+);
+
+-- Add a comment to track which colors are refill-only
+COMMENT ON TABLE filaments IS 'Filament inventory. Note: The following PLA Basic colors are refill-only (spulna must always be 0): Nardo Gray, Blue Grey, Light Gray, Brown, Beige, Bronze, Purple, Cobalt Blue, Turquoise, Bright Green, Yellow, Gold, Orange, Maroon Red';