feat(network): add ipInSubnet + IP-only network reset scope

Foundations for network-drift healing:

- ipInSubnet(ip, cidr): prefix-aware CIDR membership (pure bash), so
  stored IPs can be checked against docker's real subnet. Honours the
  actual prefix, so a healthy /16-subnet + /24-ip-range install is not
  mistaken for drift.

- dockerInstallApp now accepts reset_network="ip": re-roll the static IP
  from the current subnet but PRESERVE published host ports (clears only
  IP rows; LIBREPORTAL_RESET_IP_ONLY keeps port_allocate reusing existing
  ports). This is the heal path — a subnet move strands the IP, not the
  port, so we don't churn bookmarks/forwards/proxy upstreams. reset="true"
  still re-rolls both.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/docker/app/functions/function_install_app.sh

@@ -35,15 +35,24 @@ dockerInstallApp()
         return 1
     fi
 
-    if [[ "$reset_network" == "true" ]]; then
+    # reset_network: "true" = re-roll IPs AND host ports; "ip" = re-roll the
+    # static IP only and PRESERVE published ports (the network-heal path — a
+    # subnet move strands the IP, not the port, so don't churn bookmarks /
+    # forwards / proxy upstreams). Anything else = preserve both (normal reuse).
+    if [[ "$reset_network" == "true" || "$reset_network" == "ip" ]]; then
         export LIBREPORTAL_RESET_NETWORK=1
+        [[ "$reset_network" == "ip" ]] && export LIBREPORTAL_RESET_IP_ONLY=1
         if declare -f ipRemoveFromDatabase >/dev/null 2>&1; then
             ipRemoveFromDatabase "$app_name"
         fi
-        if declare -f portsRemoveFromDatabase >/dev/null 2>&1; then
+        if [[ "$reset_network" != "ip" ]] && declare -f portsRemoveFromDatabase >/dev/null 2>&1; then
             portsRemoveFromDatabase "$app_name"
         fi
-        isNotice "Network reset: cleared previous IP/port allocations for $app_name."
+        if [[ "$reset_network" == "ip" ]]; then
+            isNotice "Network reset (IP-only): cleared previous IP allocation for $app_name; ports preserved."
+        else
+            isNotice "Network reset: cleared previous IP/port allocations for $app_name."
+        fi
     fi
 
     # Silently update the template config so apps.json regen reflects the saved
@@ -71,5 +80,5 @@ dockerInstallApp()
         webuiGenerateLibrePortalConfig >/dev/null 2>&1 || true
     fi
 
-    unset LIBREPORTAL_RESET_NETWORK
+    unset LIBREPORTAL_RESET_NETWORK LIBREPORTAL_RESET_IP_ONLY
 }

scripts/network/ip/ip_in_subnet.sh

@@ -0,0 +1,32 @@
+#!/bin/bash
+
+# CIDR membership test: is $ip inside $cidr?
+#   ipInSubnet 10.123.154.5 10.123.154.0/24   -> 0 (in subnet)
+#   ipInSubnet 10.100.0.5    10.123.154.0/24   -> 1 (out of subnet)
+#
+# Pure-bash 32-bit integer masking that HONOURS the real prefix length, so a /16
+# genuinely contains its /24s. That matters here: the network is created with a
+# /24 ip-range but its declared subnet can be /16 (configs/network/network_docker
+# default), and a healthy "/16 subnet + /24 ip-range" install must NOT read as
+# drift. Compare stored IPs against docker's actual subnet CIDR, not a forced /24.
+# Returns 0 (in-subnet) or 1 (out-of-subnet / malformed input).
+ipInSubnet()
+{
+    local ip="$1" cidr="$2"
+    [[ "$cidr" == */* ]] || return 1
+    local base="${cidr%/*}" prefix="${cidr#*/}"
+    [[ "$prefix" =~ ^[0-9]+$ ]] && (( prefix >= 0 && prefix <= 32 )) || return 1
+
+    local re='^([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$'
+    [[ "$ip"   =~ $re ]] || return 1
+    local i1=$((10#${BASH_REMATCH[1]})) i2=$((10#${BASH_REMATCH[2]})) i3=$((10#${BASH_REMATCH[3]})) i4=$((10#${BASH_REMATCH[4]}))
+    [[ "$base" =~ $re ]] || return 1
+    local b1=$((10#${BASH_REMATCH[1]})) b2=$((10#${BASH_REMATCH[2]})) b3=$((10#${BASH_REMATCH[3]})) b4=$((10#${BASH_REMATCH[4]}))
+
+    local ip_int=$(( (i1<<24) | (i2<<16) | (i3<<8) | i4 ))
+    local base_int=$(( (b1<<24) | (b2<<16) | (b3<<8) | b4 ))
+    local mask=0
+    (( prefix > 0 )) && mask=$(( (0xFFFFFFFF << (32 - prefix)) & 0xFFFFFFFF ))
+
+    (( (ip_int & mask) == (base_int & mask) ))
+}

scripts/network/ports/allocation/port_allocate.sh

@@ -49,7 +49,10 @@ portAllocate()
 
             if [[ "${port_external_ports[$i]}" == "random" ]]; then
                 local existing_external_port=""
-                if [[ "$LIBREPORTAL_RESET_NETWORK" != "1" ]]; then
+                # Re-roll the port only on a full network reset. In IP-only mode
+                # (network heal) the port rows were left intact — reuse them so
+                # published host ports stay stable.
+                if [[ "$LIBREPORTAL_RESET_NETWORK" != "1" || "$LIBREPORTAL_RESET_IP_ONLY" == "1" ]]; then
                     existing_external_port=$(portLookupExisting "$app_name" "$full_service_name")
                 fi