fix(ui): unify colored-control text — white on all filled, both themes

The text color on filled colored controls was inconsistent: contained
primary resolved to white in both schemes, but error/success/warning/info
used a per-scheme contrastText (#fff light, #1a1a1a dark). So in DARK mode
a primary (red) button showed white text while an error (red) button —
e.g. every ConfirmDialog delete confirm, the contained "Smazat", and the
dashboard quick-action tiles — showed near-black text. "Black text on one
red button, white on another."

Unify on a single rule: every FILLED colored surface gets WHITE text/glyph
in BOTH themes. The palette .main stays bright in dark mode (it drives text,
outlined buttons and row tints), but a bright fill makes white illegible, so
filled surfaces drop to a darker fill in dark mode (new FILLED_DARK_BG, ≈ the
light-scheme shades; all ≥4.5:1 with white):
- theme MuiButton: contained error/success/warning/info -> white text +
  darker dark-mode fill (disabled state preserved).
- theme MuiChip: filled error/success/warning/info -> white label + darker
  dark-mode fill (covers StatusChip + status pills).
- StatCard icon badges: white glyph + darker dark-mode tile.

Plus two consistency cleanups:
- Detail-page "Smazat" unified to variant=outlined color=error (Offer +
  Invoice now match Order/Project/Warehouse; the contained->confirm pattern
  stays: subtle trigger, strong contained confirm dialog).
- "Zrušit filtry" reset buttons -> color=inherit (neutral), matching the
  rest of the secondary-button family (were default outlined-primary).

Neutral (color=inherit) text/outlined buttons were already correct (label =
ambient text color) and are untouched. tsc -b --noEmit, npm run build and
vitest 152/152 all clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/ui/StatCard.tsx

@@ -2,6 +2,7 @@ import type { ReactNode } from "react";
 import Box from "@mui/material/Box";
 import Typography from "@mui/material/Typography";
 import Card from "./Card";
+import { FILLED_DARK_BG } from "../theme";
 
 export type StatCardColor =
   | "default"
@@ -31,16 +32,19 @@ export default function StatCard({
   footer,
 }: StatCardProps) {
   // Solid tile + white glyph: high-contrast in both themes (the old light tint
-  // left the icon dark/low-visibility, esp. for the default variant).
+  // left the icon dark/low-visibility, esp. for the default variant). In dark
+  // mode the bright .main fill is darkened (same rule as filled buttons/chips)
+  // so the white glyph stays legible on success/warning/info/error tiles.
   const iconBg = color === "default" ? "grey.600" : `${color}.main`;
-  const iconColor = "common.white";
+  const iconDarkBg = (FILLED_DARK_BG as Record<string, { bg: string }>)[color]
+    ?.bg;
 
   return (
     <Card>
       <Box sx={{ display: "flex", alignItems: "flex-start", gap: 1.5 }}>
         {icon && (
           <Box
-            sx={{
+            sx={(theme) => ({
               display: "flex",
               alignItems: "center",
               justifyContent: "center",
@@ -48,9 +52,12 @@ export default function StatCard({
               height: 40,
               borderRadius: 2,
               bgcolor: iconBg,
-              color: iconColor,
+              color: "common.white",
               flexShrink: 0,
-            }}
+              ...(iconDarkBg
+                ? theme.applyStyles("dark", { backgroundColor: iconDarkBg })
+                : {}),
+            })}
           >
             {icon}
           </Box>