feat: Add internal firmware versioning (ph{N} suffix)

OpenWrt base version doesn't change between our config/script updates.
PARAHUB_BUILD counter creates version like 25.12.0-rc4-ph1 for tracking.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/build.sh

@@ -11,6 +11,8 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
 
 OPENWRT_VERSION="${OPENWRT_VERSION:-25.12.0-rc4}"
+PARAHUB_BUILD="1"
+FIRMWARE_VERSION="${OPENWRT_VERSION}-ph${PARAHUB_BUILD}"
 
 # ============================================================================
 # Device Database (device → target/subtarget + Image Builder profile)
@@ -174,7 +176,7 @@ build_firmware() {
     cp -a "${PROJECT_DIR}/files/"* "$tmpfiles/"
     mkdir -p "$tmpfiles/etc/parahub"
     echo "$FIRMWARE_ROLE" > "$tmpfiles/etc/parahub/role"
-    echo "$OPENWRT_VERSION" > "$tmpfiles/etc/parahub/version"
+    echo "$FIRMWARE_VERSION" > "$tmpfiles/etc/parahub/version"
     echo "$PROFILE" > "$tmpfiles/etc/parahub/profile"
     echo "$PORT_MAP" > "$tmpfiles/etc/parahub/port_map"
 
@@ -226,7 +228,7 @@ update_manifest() {
 import json, sys
 with open('$manifest') as f:
     m = json.load(f)
-m['version'] = '$OPENWRT_VERSION'
+m['version'] = '$FIRMWARE_VERSION'
 m.setdefault('devices', {})['$PROFILE'] = {
     'sysupgrade': '$filename',
     'sha256': '$sha256'
@@ -238,7 +240,7 @@ json.dump(m, sys.stdout, indent=2)
         python3 -c "
 import json, sys
 m = {
-    'version': '$OPENWRT_VERSION',
+    'version': '$FIRMWARE_VERSION',
     'devices': {
         '$PROFILE': {
             'sysupgrade': '$filename',