fix: Alpine install scripts - use separate files with valid abuild suffixes

Root cause: .apk-install is not a valid abuild suffix (lines 247-257 of abuild).
abuild expects SEPARATE files: pkgname.pre-install, .post-install, .pre-deinstall, .post-deinstall.
The old single .apk-install file caused abuild to die with "unknown install script suffix",
but CI used || true which masked the failure, so APK was built WITHOUT install scripts.

Verified on actual Alpine runner: install script suffixes now pass abuild validation.

- configs/linux-patch-api.pre-install: create dirs, set permissions (matches Debian preinst)
- configs/linux-patch-api.post-install: copy example configs, enable service (matches Debian postinst)
- configs/linux-patch-api.pre-deinstall: stop and disable service (matches Debian prerm)
- configs/linux-patch-api.post-deinstall: clean up empty dirs (matches Debian postrm)
- Removed configs/linux-patch-api.apk-install (invalid format)
- Updated build-alpine.sh: copy 4 install scripts to workspace, updated install= line in APKBUILD

configs/linux-patch-api.post-install

@@ -0,0 +1,35 @@
+#!/bin/sh
+# Alpine Linux post-install script for linux-patch-api
+# Runs after package files are laid down
+# Matches Debian postinst behavior: copy example configs, enable service
+
+# Copy example configs if they don't exist
+if [ ! -f "/etc/linux_patch_api/config.yaml" ]; then
+    if [ -f "/etc/linux_patch_api/config.yaml.example" ]; then
+        cp /etc/linux_patch_api/config.yaml.example /etc/linux_patch_api/config.yaml
+        chmod 640 /etc/linux_patch_api/config.yaml
+        chown root:root /etc/linux_patch_api/config.yaml
+    fi
+fi
+
+if [ ! -f "/etc/linux_patch_api/whitelist.yaml" ]; then
+    if [ -f "/etc/linux_patch_api/whitelist.yaml.example" ]; then
+        cp /etc/linux_patch_api/whitelist.yaml.example /etc/linux_patch_api/whitelist.yaml
+        chmod 640 /etc/linux_patch_api/whitelist.yaml
+        chown root:root /etc/linux_patch_api/whitelist.yaml
+    fi
+fi
+
+# Enable the service (but don't start automatically - admin should configure first)
+rc-update add linux-patch-api default
+
+echo ""
+echo "linux-patch-api installed successfully!"
+echo ""
+echo "Next steps:"
+echo "  1. Configure /etc/linux_patch_api/config.yaml with your settings"
+echo "  2. Place TLS certificates in /etc/linux_patch_api/certs/"
+echo "  3. Configure IP whitelist in /etc/linux_patch_api/whitelist.yaml"
+echo "  4. Start the service: rc-service linux-patch-api start"
+echo "  5. Check status: rc-service linux-patch-api status"
+echo ""