Remove drop-in config and use absolute paths in service file

Eliminate drop-in dependency by having install.sh replace
with absolute paths in the service file. EnvironmentFile loads vars from
.env directly.

Changes:
- Remove email_forwarder.service.d/ directory
- Update install.sh to sed service file for absolute paths
- Simplify README to rely on install.sh

email_forwarder.service.d/override.conf.sample

@@ -1,14 +0,0 @@
-# Sample systemd drop-in configuration for email_forwarder.service
-# Copy this file to override.conf and customize the paths for your environment.
-# For Linux: Set PROJECT_DIR to your project path, ENV_FILE to ./relative/path
-# For NixOS: Set PROJECT_DIR to /var/lib/email_forwarder, ENV_FILE to /etc/email_forwarder/.env
-
-[Service]
-# Path to the email forwarder project directory
-Environment=PROJECT_DIR=/path/to/your/email_forwarder
-
-# Path to the .env file (default: ./.env relative to PROJECT_DIR)
-Environment=ENV_FILE=./.env
-
-# Load environment variables from the .env file
-EnvironmentFile=${PROJECT_DIR}/.env

install.sh

@@ -53,12 +53,8 @@ setup_systemd() {
     # Copy service files
     cp *.service *.timer "$HOME/.config/systemd/user/"
 
-    # Copy and configure drop-in
-    mkdir -p "$HOME/.config/systemd/user/email_forwarder.service.d"
-    cp email_forwarder.service.d/override.conf.sample "$HOME/.config/systemd/user/email_forwarder.service.d/override.conf"
-
-    # Replace placeholders
-    sed -i "s|/path/to/your/email_forwarder|$PROJECT_DIR|g" "$HOME/.config/systemd/user/email_forwarder.service.d/override.conf"
+    # Replace placeholders in service file
+    sed -i "s|\${PROJECT_DIR}|$PROJECT_DIR|g" "$HOME/.config/systemd/user/email_forwarder.service"
 
     # Reload systemd
     systemctl --user daemon-reload