feat: skin engine + Twenty CRM theme for iistwin

- Add client/src/themes/ with tokens, built-in skins (iistwin, twenty, omegaprom)
- Add ThemeProvider with data-skin/data-theme and runtime CSS for custom skins
- Add npm run skins:generate script for build-time CSS generation
- Add organization_skins table, migration and CRUD API
- Add activeSkinId to organizations and expose it in /api/auth/me
- Add skin switcher in /profile and admin skin editor in /settings/appearance
- Adapt index.css hardcoded colors to skin tokens
- Update AGENTS.md and Obsidian notes

shared/schema.ts

@@ -32,12 +32,33 @@ export const organizations = pgTable("organizations", {
   displayName: varchar("display_name", { length: 200 }).notNull(),
   logoUrl: varchar("logo_url", { length: 500 }),
   themeColor: varchar("theme_color", { length: 7 }).default("#1976d2"),
+  activeSkinId: varchar("active_skin_id", { length: 50 }).default("iistwin"),
   createdAt: timestamp("created_at").defaultNow(),
   updatedAt: timestamp("updated_at").defaultNow(),
   isActive: boolean("is_active").default(true),
   billingBlocked: boolean("billing_blocked").default(false),
 });
 
+// Organization skins
+export const organizationSkins = pgTable("organization_skins", {
+  id: serial("id").primaryKey(),
+  organizationId: integer("organization_id").notNull().references(() => organizations.id, { onDelete: "cascade" }),
+  skinId: varchar("skin_id", { length: 50 }).notNull(),
+  name: varchar("name", { length: 100 }).notNull(),
+  description: text("description"),
+  tokens: jsonb("tokens").notNull(),
+  isEditable: boolean("is_editable").default(true),
+  isActive: boolean("is_active").default(false),
+  createdBy: integer("created_by").notNull().references(() => users.id, { onDelete: "cascade" }),
+  createdAt: timestamp("created_at").defaultNow(),
+  updatedAt: timestamp("updated_at").defaultNow(),
+}, (table) => ({
+  uniqueOrgSkin: unique().on(table.organizationId, table.skinId),
+}));
+
+export type OrganizationSkin = typeof organizationSkins.$inferSelect;
+export type InsertOrganizationSkin = typeof organizationSkins.$inferInsert;
+
 // Billing settings per organization (1:1)
 export const organizationBilling = pgTable("organization_billing", {
   organizationId: integer("organization_id").primaryKey().references(() => organizations.id, { onDelete: "cascade" }),
@@ -678,6 +699,18 @@ export const messageReads = pgTable("message_reads", {
 export const organizationsRelations = relations(organizations, ({ many }) => ({
   users: many(users),
   forms: many(forms),
+  skins: many(organizationSkins),
+}));
+
+export const organizationSkinsRelations = relations(organizationSkins, ({ one }) => ({
+  organization: one(organizations, {
+    fields: [organizationSkins.organizationId],
+    references: [organizations.id],
+  }),
+  createdByUser: one(users, {
+    fields: [organizationSkins.createdBy],
+    references: [users.id],
+  }),
 }));
 
 export const usersRelations = relations(users, ({ one, many }) => ({