fix(brand): the tab was showing a different mark from every page

Measured, not eyeballed. logo.png — what the site header, the footer, the deck,
the one-pager and the social card all draw — is 44.8% violet #6E54FF and 42.6%
amber #FEAD44. The icons were 85% violet background and 10.9% white mark, with
no amber at all. So the browser tab showed a one-colour silhouette while every
surface underneath it showed a two-colour one, and the split is the idea: two
parties on two sides of one debt.

It was also failing at the size that matters. White on violet has so little
edge left after downscaling that at 16px it collapsed into a violet blob.

docs/build-icons.py now derives all three from the one mark, on the site's own
--color-surface. Checked against a light and a dark tab bar at 32/24/16px: the
square is load-bearing, because on transparent the violet half disappears into
dark browser chrome while the amber survives — which would have traded one
inconsistency for a worse one. apple-icon is deliberately full-bleed, since iOS
applies its own mask and rounding it here leaves white notches in the corners.

Everything else was already consistent: header, footer and pitch nav on all
three routes, both deck footers (the accent slide's white mono mark is the
intended inversion), the one-pager and the OpenGraph card.

Author: 0xFearless-1

dashboard/src/app/apple-icon.png

@@ -0,0 +1,69 @@
+#!/usr/bin/env python3
+"""Regenerate the browser and app icons from the one brand mark.
+
+The site, the deck, the one-pager and the social card all draw the same file:
+dashboard/public/logo.png — a violet half and an amber half, roughly 45/43 of the
+mark's pixels. The split is the idea: two parties, two sides of one debt.
+
+The icons did not. They were a white silhouette on a solid violet square, so the tab
+showed a one-colour mark while every page showed a two-colour one, and the amber was
+absent entirely. Worse at 16px: white-on-violet has so little edge left after
+downscaling that it collapses into a violet blob.
+
+So the icons are derived from the same mark, on the site's own surface colour. Checked
+against both a light and a dark tab bar at 16px: the square is load-bearing, because a
+transparent background loses the violet half against dark chrome.
+
+    python3 docs/build-icons.py
+"""
+
+import pathlib
+from PIL import Image, ImageDraw
+
+ROOT = pathlib.Path(__file__).resolve().parent.parent
+LOGO = ROOT / "dashboard" / "public" / "logo.png"
+APP = ROOT / "dashboard" / "src" / "app"
+
+# --color-surface from globals.css: the same near-white the mark sits on everywhere else.
+SURFACE = (247, 248, 252, 255)
+PAD = 0.13  # breathing room so the mark does not touch the corner radius
+RADIUS = 0.22
+
+
+def render(size: int, rounded: bool = True, pad: float = PAD) -> Image.Image:
+    logo = Image.open(LOGO).convert("RGBA")
+    canvas = Image.new("RGBA", (size, size), (0, 0, 0, 0))
+
+    square = Image.new("RGBA", (size, size), SURFACE)
+    if rounded:
+        mask = Image.new("L", (size, size), 0)
+        ImageDraw.Draw(mask).rounded_rectangle(
+            [0, 0, size - 1, size - 1], radius=int(size * RADIUS), fill=255
+        )
+        canvas.paste(square, (0, 0), mask)
+    else:
+        canvas.paste(square, (0, 0))
+
+    inner = int(size * (1 - 2 * pad))
+    mark = logo.resize((inner, inner), Image.LANCZOS)
+    offset = (size - inner) // 2
+    canvas.paste(mark, (offset, offset), mark)
+    return canvas
+
+
+def main() -> None:
+    render(512).save(APP / "icon.png")
+    print(f"  icon.png        512x512  rounded")
+
+    # Full-bleed: iOS applies its own mask, and rounding it here would leave the
+    # corners transparent inside Apple's rounding — a white notch on every home screen.
+    render(180, rounded=False, pad=0.16).save(APP / "apple-icon.png")
+    print(f"  apple-icon.png  180x180  full-bleed for iOS masking")
+
+    sizes = [(16, 16), (32, 32), (48, 48)]
+    render(256).save(APP / "favicon.ico", sizes=sizes)
+    print(f"  favicon.ico     {', '.join(f'{w}x{h}' for w, h in sizes)}")
+
+
+if __name__ == "__main__":
+    main()