daedalus-v4l2-dkms: loud warning when DKMS build doesn't land

Sonnet pre-deployment review caught a BLOCKER: on a fresh higgs
(Debian 13 / Pi CM5) install without the RPi kernel headers
pre-installed, the postinst's `dkms autoinstall || true` silently
swallowed the build failure. Package appeared installed but the
.ko was absent; `modprobe daedalus_v4l2` then failed and the
entire stack was dead with no clear pointer to the cause.

Fix in both ecosystems:

debian/daedalus-v4l2-dkms/build-deb.sh:
- After `dkms autoinstall`, verify the post-condition with
  `dkms status -m daedalus_v4l2 -v VER -k $(uname -r)`.
- If the module isn't 'installed' / 'loaded' for the running
  kernel, emit a yellow-bolded ANSI warning naming the most
  likely cause (kernel headers package missing) and the exact
  recovery steps (linux-headers-rpi-2712 for RPi or
  linux-headers-$KERNELVER for Debian generic, then
  `dkms autoinstall` + `modprobe`).
- Colour only on TTY; the warning is unconditional regardless.

arch/daedalus-v4l2-dkms/:
- New daedalus-v4l2-dkms.install with post_install +
  post_upgrade hooks that run the same `dkms status` check.
- post_upgrade catches the case where a kernel-headers package
  was uninstalled / pruned between upgrades, silently
  regressing the build.
- Wired into the PKGBUILD via install="${pkgname}.install".

Both versions point at the actual repair commands rather than
just saying "build failed", so the user is one apt/pacman away
from a working stack instead of debugging dkms internals.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

arch/daedalus-v4l2-dkms/PKGBUILD

@@ -28,10 +28,13 @@ url="https://git.reauktion.de/reauktion/daedalus-v4l2"
 license=('GPL-2.0-or-later')
 depends=('dkms')
 makedepends=('git')
+install="${pkgname}.install"
 
 source=("git+https://git.reauktion.de/reauktion/daedalus-v4l2.git#commit=${_commit}"
-        "dkms.conf")
+        "dkms.conf"
+        "${pkgname}.install")
 sha256sums=('SKIP'
+            'SKIP'
             'SKIP')
 
 pkgver() {