feat: add Stalwart Mail Server and FoundationDB library packages

- add stalwart: main mail server with systemd integration and user management
- add stalwart-cli: command line interface tool for server administration
- add stalwart-foundationdb: FoundationDB-enabled version with proper dependencies
- add libfoundationdb: FoundationDB client library (libfdb_c.so) package

All packages include proper conflict resolution, systemd services, and follow
repository packaging conventions. stalwart and stalwart-foundationdb are
mutually exclusive to prevent installation conflicts.

rpms/stalwart/resources/scripts/postinstall.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+
+# Create default configuration if it doesn't exist
+if [ ! -f /opt/stalwart/etc/config.toml ]; then
+    cat > /opt/stalwart/etc/config.toml << 'EOF'
+# Stalwart Mail Server Configuration
+# This is a minimal configuration file. Please customize according to your needs.
+# Full documentation: https://stalw.art/docs/
+
+[server]
+hostname = "localhost"
+
+[server.listener.smtp]
+bind = ["127.0.0.1:25"]
+protocol = "smtp"
+
+[server.listener.submission]
+bind = ["127.0.0.1:587"]
+protocol = "smtp"
+
+[server.listener.imap]
+bind = ["127.0.0.1:143"]
+protocol = "imap"
+
+[server.listener.http]
+bind = ["127.0.0.1:8080"]
+protocol = "http"
+
+[storage]
+data = "sqlite"
+fts = "sqlite"
+blob = "fs"
+lookup = "sqlite"
+directory = "internal"
+
+[store."sqlite"]
+type = "sqlite"
+path = "/var/lib/stalwart/stalwart.db"
+
+[store."fs"]
+type = "fs"
+path = "/var/lib/stalwart/blobs"
+
+[directory."internal"]
+type = "internal"
+store = "sqlite"
+EOF
+
+    chown stalwart:stalwart /opt/stalwart/etc/config.toml
+    chmod 600 /opt/stalwart/etc/config.toml
+fi
+
+# Reload systemd
+systemctl daemon-reload

rpms/stalwart/resources/scripts/postremove.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+# Reload systemd after service file removal
+systemctl daemon-reload
+
+# Note: We don't remove user data, logs, or configuration files
+# to preserve user data in case of reinstallation

rpms/stalwart/resources/scripts/preinstall.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+# Create stalwart user and group
+if ! getent group stalwart >/dev/null; then
+    groupadd -r stalwart
+fi
+
+if ! getent passwd stalwart >/dev/null; then
+    useradd -r -g stalwart -d /opt/stalwart -s /sbin/nologin -c "Stalwart Mail Server" stalwart
+fi
+
+# Create required directories
+mkdir -p /opt/stalwart/{bin,etc,data,logs}
+mkdir -p /var/lib/stalwart
+mkdir -p /var/log/stalwart
+
+# Set ownership
+chown -R stalwart:stalwart /opt/stalwart
+chown -R stalwart:stalwart /var/lib/stalwart
+chown -R stalwart:stalwart /var/log/stalwart

rpms/stalwart/resources/scripts/preremove.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+# Stop and disable the service if it's running
+if systemctl is-enabled stalwart.service >/dev/null 2>&1; then
+    systemctl stop stalwart.service
+    systemctl disable stalwart.service
+fi