feat: open-source under AGPL-3.0, redesign UI to grayscale palette, add uncategorize API, fix VAT account names

Add LICENSE (AGPL-3.0-or-later), CONTRIBUTING.md, SECURITY.md, DCO, and NOTICE files.
Rewrite README for open-source audience with self-hosting instructions.
Redesign color palette to grayscale chrome theme across all components.
Add transaction uncategorize API route with tests.
Fix VAT account name mismatches in migration 052.
Improve import page with SIE file support and loading skeleton.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/globals.css

@@ -4,59 +4,61 @@
 
 :root {
   color-scheme: light;
-  /* Clean Slate — Modern ERP Palette */
+  /* Grayscale Chrome Palette */
 
-  --background: 220 14% 96%;              /* Cool off-white #F2F4F7 */
-  --foreground: 224 12% 13%;              /* Deep slate #1D2029 */
+  --background: 0 0% 97%;
+  --foreground: 0 0% 9%;
 
-  --card: 0 0% 100%;                      /* Pure white */
-  --card-foreground: 224 12% 13%;
+  --card: 0 0% 100%;
+  --card-foreground: 0 0% 9%;
 
   --popover: 0 0% 100%;
-  --popover-foreground: 224 12% 13%;
+  --popover-foreground: 0 0% 9%;
 
-  /* Primary — Refined navy-blue */
-  --primary: 222 47% 35%;                 /* #304D83 */
+  --primary: 0 0% 15%;
   --primary-foreground: 0 0% 100%;
 
-  /* Secondary — Cool pale gray */
-  --secondary: 220 13% 93%;               /* #EBEDF1 */
-  --secondary-foreground: 224 12% 13%;
+  --secondary: 0 0% 94%;
+  --secondary-foreground: 0 0% 9%;
 
-  /* Muted — Neutral gray */
-  --muted: 218 12% 91%;                   /* #E3E6EB */
-  --muted-foreground: 218 8% 46%;         /* #6B7280 */
+  --muted: 0 0% 92%;
+  --muted-foreground: 0 0% 45%;
 
-  /* Accent — Clear blue for interactive highlights */
-  --accent: 213 72% 50%;                  /* #2373D8 */
-  --accent-foreground: 0 0% 100%;
+  --accent: 0 0% 92%;
+  --accent-foreground: 0 0% 9%;
 
-  /* Destructive — Clean red */
-  --destructive: 0 68% 50%;               /* #D63232 */
+  --destructive: 6 36% 48%;               /* Muted terracotta */
   --destructive-foreground: 0 0% 100%;
 
-  /* Borders & Input */
-  --border: 218 14% 89%;                  /* #DEE1E7 */
-  --input: 218 14% 89%;
-  --ring: 222 47% 35%;
+  --border: 0 0% 90%;
+  --input: 0 0% 90%;
+  --ring: 0 0% 15%;
 
   /* Radius */
   --radius: 0.5rem;
 
-  /* Success — Clean green */
-  --success: 152 48% 38%;                 /* #329460 */
+  /* Success — Sage green */
+  --success: 155 25% 40%;
   --success-foreground: 0 0% 100%;
 
-  /* Warning — Clear amber */
-  --warning: 38 92% 50%;                  /* #F59E0B */
-  --warning-foreground: 224 12% 13%;
+  /* Warning — Muted ochre */
+  --warning: 38 55% 50%;
+  --warning-foreground: 0 0% 9%;
+
+  --warm-accent: 38 45% 52%;
+
+  /* Chart colors */
+  --chart-1: 155 25% 40%;
+  --chart-2: 6 36% 48%;
+  --chart-3: 38 55% 50%;
+  --chart-4: 0 0% 50%;
 
   /* Custom tokens */
   --font-display: var(--font-fraunces), Georgia, serif;
   --font-body: var(--font-geist-sans), system-ui, sans-serif;
 
   /* Shadows — cool-toned */
-  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.04);
+  --shadow-sm: 0 1px 3px rgba(15, 23, 42, 0.06), 0 1px 2px rgba(15, 23, 42, 0.04);
   --shadow-md: 0 4px 12px rgba(15, 23, 42, 0.06);
   --shadow-lg: 0 12px 40px rgba(15, 23, 42, 0.08);
 
@@ -71,39 +73,46 @@
 .dark {
   color-scheme: dark;
 
-  --background: 222 16% 10%;
-  --foreground: 216 12% 90%;
+  --background: 0 0% 7%;
+  --foreground: 0 0% 87%;
 
-  --card: 222 14% 13%;
-  --card-foreground: 216 12% 90%;
+  --card: 0 0% 10%;
+  --card-foreground: 0 0% 87%;
 
-  --popover: 222 14% 13%;
-  --popover-foreground: 216 12% 90%;
+  --popover: 0 0% 10%;
+  --popover-foreground: 0 0% 87%;
 
-  --primary: 222 50% 55%;
-  --primary-foreground: 0 0% 100%;
+  --primary: 0 0% 85%;
+  --primary-foreground: 0 0% 7%;
 
-  --secondary: 220 14% 18%;
-  --secondary-foreground: 216 12% 90%;
+  --secondary: 0 0% 14%;
+  --secondary-foreground: 0 0% 87%;
 
-  --muted: 220 12% 20%;
-  --muted-foreground: 218 8% 55%;
+  --muted: 0 0% 16%;
+  --muted-foreground: 0 0% 50%;
 
-  --accent: 213 72% 58%;
-  --accent-foreground: 0 0% 100%;
+  --accent: 0 0% 16%;
+  --accent-foreground: 0 0% 87%;
 
-  --destructive: 0 62% 55%;
+  --destructive: 6 32% 56%;
   --destructive-foreground: 0 0% 100%;
 
-  --border: 220 12% 22%;
-  --input: 220 12% 22%;
-  --ring: 222 50% 55%;
+  --border: 0 0% 18%;
+  --input: 0 0% 18%;
+  --ring: 0 0% 85%;
 
-  --success: 152 44% 45%;
+  --success: 155 22% 48%;
   --success-foreground: 0 0% 100%;
 
-  --warning: 38 85% 55%;
-  --warning-foreground: 224 12% 13%;
+  --warning: 38 50% 55%;
+  --warning-foreground: 0 0% 9%;
+
+  --warm-accent: 38 42% 58%;
+
+  --chart-1: 155 22% 48%;
+  --chart-2: 6 32% 56%;
+  --chart-3: 38 50% 55%;
+  --chart-4: 0 0% 55%;
 
   --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.25);
   --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.35);
@@ -134,6 +143,7 @@
   --color-success-foreground: hsl(var(--success-foreground));
   --color-warning: hsl(var(--warning));
   --color-warning-foreground: hsl(var(--warning-foreground));
+  --color-warm-accent: hsl(var(--warm-accent));
   --radius-lg: var(--radius);
   --radius-md: calc(var(--radius) - 2px);
   --radius-sm: calc(var(--radius) - 4px);
@@ -271,7 +281,7 @@ h1, h2, h3 {
 .focus-ring:focus-visible {
   outline: none;
   box-shadow: 0 0 0 2px hsl(var(--background)),
-              0 0 0 4px hsl(var(--primary) / 0.3);
+              0 0 0 4px hsl(var(--primary) / 0.35);
 }
 
 /* Custom scrollbar - minimal */