Initial setup: Matrix Synapse + Element Web

- docker-compose.yml with Synapse, PostgreSQL 16, Element Web
- Element config pointing to chat.dshkabatur.ru
- .gitignore for data directories

Co-authored-by: Cursor <cursoragent@cursor.com>

element-config.json

@@ -0,0 +1,18 @@
+{
+    "default_server_config": {
+        "m.homeserver": {
+            "base_url": "https://chat.dshkabatur.ru",
+            "server_name": "chat.dshkabatur.ru"
+        }
+    },
+    "brand": "Dshkabatur Chat",
+    "default_theme": "dark",
+    "room_directory": {
+        "servers": ["chat.dshkabatur.ru"]
+    },
+    "show_labs_settings": false,
+    "default_country_code": "RU",
+    "setting_defaults": {
+        "breadcrumbs": true
+    }
+}