Implement multi-timeframe support for indicators

- Enhanced the `UserIndicator` class to include an optional `timeframe` attribute for custom indicator timeframes.
- Updated the `get_indicator_data` method in `MarketDataIntegrator` to fetch and calculate indicators based on the specified timeframe, ensuring proper data alignment and handling.
- Modified the `ChartBuilder` to pass the correct DataFrame for plotting indicators with different timeframes.
- Added UI elements in the indicator modal for selecting timeframes, improving user experience.
- Updated relevant JSON templates to include the new `timeframe` field for all indicators.
- Refactored the `prepare_chart_data` function to ensure it returns a DataFrame with a `DatetimeIndex` for consistent calculations.

This commit enhances the flexibility and usability of the indicator system, allowing users to analyze data across various timeframes.

config/indicators/user_indicators/ema_b869638d.json

@@ -0,0 +1,20 @@
+{
+  "id": "ema_b869638d",
+  "name": "EMA 12 (15 minutes)",
+  "description": "",
+  "type": "ema",
+  "display_type": "overlay",
+  "parameters": {
+    "period": 12
+  },
+  "styling": {
+    "color": "#007bff",
+    "line_width": 2,
+    "opacity": 1.0,
+    "line_style": "solid"
+  },
+  "timeframe": "15m",
+  "visible": true,
+  "created_date": "2025-06-06T06:56:54.181578+00:00",
+  "modified_date": "2025-06-06T06:56:54.181578+00:00"
+}

config/indicators/user_indicators/ema_bfbf3a1d.json

@@ -0,0 +1,20 @@
+{
+  "id": "ema_bfbf3a1d",
+  "name": "EMA 12 (5 minutes)",
+  "description": "",
+  "type": "ema",
+  "display_type": "overlay",
+  "parameters": {
+    "period": 12
+  },
+  "styling": {
+    "color": "#007bff",
+    "line_width": 2,
+    "opacity": 1.0,
+    "line_style": "solid"
+  },
+  "timeframe": "5m",
+  "visible": true,
+  "created_date": "2025-06-06T07:02:34.613543+00:00",
+  "modified_date": "2025-06-06T07:02:34.613543+00:00"
+}

config/indicators/user_indicators/macd_307935a7.json

@@ -15,7 +15,8 @@
     "opacity": 1.0,
     "line_style": "solid"
   },
+  "timeframe": "1h",
   "visible": true,
   "created_date": "2025-06-04T04:16:35.459602+00:00",
-  "modified_date": "2025-06-04T04:16:35.459602+00:00"
+  "modified_date": "2025-06-06T07:03:58.642238+00:00"
 }