fix(email): create missing email template and decouple email destination settings

- Create app/templates/email/default.html (fixes 'default.html not found' error)
- Add DEST_EMAIL_* settings to app/config.py (decoupled from shared EMAIL_* settings)
- Update upload_to_email task to use dest_email_* settings exclusively
- Update _should_upload_to_email() to check dest_email_* settings
- Update config validator, providers, and settings_service for dest_email_*
- Update .env.demo and docs/ConfigurationGuide.md
- Update all tests to use dest_email_* settings where appropriate"

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/utils/settings_service.py

@@ -917,7 +917,7 @@ SETTING_METADATA = {
     # Email Settings
     "email_host": {
         "category": "Email",
-        "description": "SMTP server hostname",
+        "description": "SMTP server hostname (shared – used for password reset and verification emails)",
         "type": "string",
         "sensitive": False,
         "required": False,
@@ -965,7 +965,64 @@ SETTING_METADATA = {
     },
     "email_default_recipient": {
         "category": "Email",
-        "description": "Default recipient email address",
+        "description": "Default recipient email address (shared – used for system notifications)",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    # Email Destination Settings (dedicated SMTP for document delivery)
+    "dest_email_host": {
+        "category": "Email Destination",
+        "description": "SMTP server hostname for document delivery (separate from shared email settings)",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "dest_email_port": {
+        "category": "Email Destination",
+        "description": "SMTP port for document delivery (default: 587)",
+        "type": "integer",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "dest_email_username": {
+        "category": "Email Destination",
+        "description": "SMTP username for document delivery",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "dest_email_password": {
+        "category": "Email Destination",
+        "description": "SMTP password for document delivery",
+        "type": "string",
+        "sensitive": True,
+        "required": False,
+        "restart_required": False,
+    },
+    "dest_email_use_tls": {
+        "category": "Email Destination",
+        "description": "Use TLS encryption for document delivery SMTP",
+        "type": "boolean",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "dest_email_sender": {
+        "category": "Email Destination",
+        "description": "From address for document delivery emails (defaults to dest_email_username)",
+        "type": "string",
+        "sensitive": False,
+        "required": False,
+        "restart_required": False,
+    },
+    "dest_email_default_recipient": {
+        "category": "Email Destination",
+        "description": "Default recipient email for document delivery when none is specified",
         "type": "string",
         "sensitive": False,
         "required": False,