docs: add modeGroups feature to award system specification

Document the modeGroups property for award definitions, which allows
creating convenient multi-mode filters in the award detail view.

Co-Authored-By: Claude <noreply@anthropic.com>

docs/AWARD-SYSTEM-SPECIFICATION.md

@@ -71,6 +71,7 @@ Every award definition is a JSON object with the following structure:
 | `caption` | string | Yes | Detailed explanation of award requirements |
 | `category` | string | Yes | Grouping category for UI organization (e.g., "dxcc", "darc", "vucc") |
 | `rules` | object | Yes | Award calculation rules (see Rule Types below) |
+| `modeGroups` | object | No | Mode group definitions for award detail view filtering (see Mode Groups below) |
 
 ---
 
@@ -456,6 +457,85 @@ This creates: DLD 80m CW (only QSOs on 80m band AND CW mode count).
 
 ---
 
+## Mode Groups
+
+Mode groups allow awards to define convenient multi-mode filters for the award detail view. This feature enables users to filter by multiple modes at once (e.g., all digital modes combined).
+
+### Structure
+
+```json
+{
+  "modeGroups": {
+    "Group Display Name": ["mode1", "mode2", "mode3"],
+    "Another Group": ["modeA", "modeB"]
+  }
+}
+```
+
+### Properties
+
+| Property | Type | Required | Description |
+|----------|------|----------|-------------|
+| Key | string | Yes | Display name shown in mode filter dropdown |
+| Value | array | Yes | Array of mode strings to include in the group |
+
+### Behavior
+
+- **Location**: Defined at award root level (not in `rules`)
+- **Optional**: Awards without `modeGroups` work as before (backward compatible)
+- **UI Integration**: Creates entries in mode filter dropdown with visual separator
+- **Filtering**: Selecting a mode group filter shows QSOs matching ANY mode in the group
+
+### Example: DXCC with Mode Groups
+
+```json
+{
+  "id": "dxcc",
+  "name": "DXCC",
+  "description": "Confirm 100 DXCC entities on HF bands",
+  "caption": "Contact and confirm 100 different DXCC entities on HF bands (160m-10m).",
+  "category": "dxcc",
+  "modeGroups": {
+    "Digi-Modes": ["FT8", "FT4", "MFSK", "PSK31", "RTTY", "JT65", "JT9"],
+    "Classic Digi-Modes": ["PSK31", "RTTY", "JT65", "JT9"],
+    "Mixed-Mode w/o WSJT-Modes": ["PSK31", "RTTY", "AM", "SSB", "FM", "CW"],
+    "Phone-Modes": ["AM", "SSB", "FM"]
+  },
+  "rules": {
+    "type": "entity",
+    "entityType": "dxcc",
+    "target": 100,
+    "allowed_bands": ["160m", "80m", "60m", "40m", "30m", "20m", "17m", "15m", "12m", "10m"]
+  }
+}
+```
+
+### UI Display
+
+In the award detail view, the mode filter dropdown shows:
+- Mixed Mode (default - aggregates all modes by band)
+- ───── (visual separator)
+- Digi-Modes
+- Classic Digi-Modes
+- Mixed-Mode w/o WSJT-Modes
+- Phone-Modes
+- ───── (visual separator)
+- CW (individual modes)
+- FT8
+- SSB
+- etc.
+
+### Common Mode Group Patterns
+
+| Group Name | Modes | Use Case |
+|------------|-------|----------|
+| Digi-Modes | FT8, FT4, MFSK, PSK31, RTTY, JT65, JT9 | All digital modes |
+| Classic Digi-Modes | PSK31, RTTY, JT65, JT9 | Pre-WSJT digital modes |
+| Phone-Modes | AM, SSB, FM | All voice modes |
+| Mixed-Mode w/o WSJT | PSK31, RTTY, AM, SSB, FM, CW | Traditional mixed mode award |
+
+---
+
 ## QSO Database Schema
 
 The award system relies on QSO records with specific fields.