docs: rewrite README with structured overview and quick start guide

Replaces the minimal project description with a comprehensive README
including a component overview table, quick start instructions, common
Ansible operations, and links to detailed documentation. Aligns with
Red Panda Approval™ standards.

ansible/pplg/config_local.py.j2

@@ -0,0 +1,55 @@
+# PgAdmin4 Local Configuration - Managed by Ansible
+# Gunicorn-based deployment (no Apache) with Casdoor OAuth SSO
+# Red Panda Approved
+
+import os
+
+# Server settings
+DEFAULT_SERVER = '0.0.0.0'
+DEFAULT_SERVER_PORT = {{pgadmin_port}}
+
+# Data directory
+DATA_DIR = '{{pgadmin_data_dir}}'
+SESSION_DB_PATH = os.path.join(DATA_DIR, 'sessions')
+STORAGE_DIR = os.path.join(DATA_DIR, 'storage')
+SQLITE_PATH = os.path.join(DATA_DIR, 'pgadmin4.db')
+
+# Log settings
+LOG_FILE = '{{pgadmin_log_dir}}/pgadmin4.log'
+
+# Default admin credentials (for initial setup)
+SETUP_EMAIL = '{{pgadmin_email}}'
+SETUP_PASSWORD = '{{pgadmin_password}}'
+
+# Authentication - OAuth2 (Casdoor) + internal fallback
+AUTHENTICATION_SOURCES = ['oauth2', 'internal']
+
+# Master password disabled (use OAuth)
+MASTER_PASSWORD_REQUIRED = False
+
+# Reverse proxy settings (Titania HAProxy -> Prospero HAProxy -> Gunicorn)
+ENHANCED_COOKIE_PROTECTION = False
+PROXY_X_FOR_COUNT = 2
+PROXY_X_PROTO_COUNT = 2
+PROXY_X_HOST_COUNT = 2
+X_FRAME_OPTIONS = 'SAMEORIGIN'
+SESSION_COOKIE_SECURE = True
+SESSION_COOKIE_SAMESITE = 'Lax'
+WTF_CSRF_SSL_STRICT = False
+
+# OAuth2 Configuration (Casdoor OIDC)
+OAUTH2_AUTO_CREATE_USER = True
+OAUTH2_CONFIG = [{
+    'OAUTH2_NAME': 'Casdoor',
+    'OAUTH2_DISPLAY_NAME': 'Casdoor SSO',
+    'OAUTH2_CLIENT_ID': '{{pgadmin_oauth_client_id}}',
+    'OAUTH2_CLIENT_SECRET': '{{pgadmin_oauth_client_secret}}',
+    'OAUTH2_TOKEN_URL': 'https://id.ouranos.helu.ca/api/login/oauth/access_token',
+    'OAUTH2_AUTHORIZATION_URL': 'https://id.ouranos.helu.ca/login/oauth/authorize',
+    'OAUTH2_API_BASE_URL': 'https://id.ouranos.helu.ca/',
+    'OAUTH2_USERINFO_ENDPOINT': 'api/userinfo',
+    'OAUTH2_SERVER_METADATA_URL': 'https://id.ouranos.helu.ca/.well-known/openid-configuration',
+    'OAUTH2_SCOPE': 'openid profile email',
+    'OAUTH2_ICON': 'fa-openid',
+    'OAUTH2_BUTTON_COLOR': '#2db7f5',
+}]