docs: update CLAUDE.md with DLD award variants documentation

- Added filter support to DOK award type description
- Added new section "Creating DLD Award Variants" with examples
- Documented available filter operators and fields
- Examples include DLD 80m, DLD CW, and DLD 80m CW

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -146,8 +146,10 @@ The award system is JSON-driven and located in `award-definitions/` directory. E
 2. **`dok`**: Count unique DOK (DARC Ortsverband Kennung) combinations
    - `target`: Number required
    - `confirmationType`: "dcl" (DARC Community Logbook)
+   - `filters`: Optional filters (band, mode, etc.) for award variants
    - Counts unique (DOK, band, mode) combinations
    - Only DCL-confirmed QSOs count
+   - Example variants: DLD 80m, DLD CW, DLD 80m CW
 
 3. **`points`**: Point-based awards
    - `stations`: Array of {callsign, points}
@@ -202,6 +204,14 @@ The award system is JSON-driven and located in `award-definitions/` directory. E
 - `POST /api/dcl/sync`: Queue DCL sync job
 - `GET /api/jobs/:jobId`: Get job status
 - `GET /api/jobs/active`: Get active job for current user
+- `GET /*`: Serves static files from `src/frontend/build/` with SPA fallback
+
+**SPA Routing**: The backend serves the SvelteKit frontend build from `src/frontend/build/`.
+- Paths with file extensions (`.js`, `.css`, etc.) are served as static files
+- Paths without extensions (e.g., `/qsos`, `/awards`) are served `index.html` for client-side routing
+- Common missing files like `/favicon.ico` return 404 immediately
+- If frontend build is missing entirely, returns a user-friendly 503 HTML page
+- Prevents ugly Bun error pages when accessing client-side routes via curl or non-JS clients
 
 **DCL Service**: `src/backend/services/dcl.service.js`
 - `fetchQSOsFromDCL(dclApiKey, sinceDate)`: Fetch from DCL API
@@ -277,6 +287,77 @@ To add a new award:
 6. Update documentation in `docs/DOCUMENTATION.md`
 7. Test with sample QSO data
 
+### Creating DLD Award Variants
+
+The DOK award type supports filters to create award variants. Examples:
+
+**DLD on 80m** (`dld-80m.json`):
+```json
+{
+  "id": "dld-80m",
+  "name": "DLD 80m",
+  "description": "Confirm 100 unique DOKs on 80m",
+  "caption": "Contact 100 different DOKs on the 80m band.",
+  "category": "darc",
+  "rules": {
+    "type": "dok",
+    "target": 100,
+    "confirmationType": "dcl",
+    "displayField": "darcDok",
+    "filters": {
+      "operator": "AND",
+      "filters": [
+        { "field": "band", "operator": "eq", "value": "80m" }
+      ]
+    }
+  }
+}
+```
+
+**DLD in CW mode** (`dld-cw.json`):
+```json
+{
+  "rules": {
+    "type": "dok",
+    "target": 100,
+    "confirmationType": "dcl",
+    "filters": {
+      "operator": "AND",
+      "filters": [
+        { "field": "mode", "operator": "eq", "value": "CW" }
+      ]
+    }
+  }
+}
+```
+
+**DLD on 80m using CW** (combined filters, `dld-80m-cw.json`):
+```json
+{
+  "rules": {
+    "type": "dok",
+    "target": 100,
+    "confirmationType": "dcl",
+    "filters": {
+      "operator": "AND",
+      "filters": [
+        { "field": "band", "operator": "eq", "value": "80m" },
+        { "field": "mode", "operator": "eq", "value": "CW" }
+      ]
+    }
+  }
+}
+```
+
+**Available filter operators**:
+- `eq`: equals
+- `ne`: not equals
+- `in`: in array
+- `nin`: not in array
+- `contains`: contains substring
+
+**Available filter fields**: Any QSO field (band, mode, callsign, grid, state, satName, etc.)
+
 ### Confirmation Systems
 
 - **LoTW (Logbook of The World)**: ARRL's confirmation system
@@ -316,11 +397,14 @@ Both LoTW and DCL return data in ADIF (Amateur Data Interchange Format):
 
 ### Recent Commits
 
-- **Uncommitted**: fix: logger debug level not working
-  - Fixed bug where debug logs weren't showing due to falsy value handling
-  - Changed `||` to `??` in logger config to properly handle log level 0 (debug)
-  - Added `.env` file with `LOG_LEVEL=debug` for development
-  - Debug logs now show DCL API request parameters with redacted API key
+- `7201446`: fix: return proper HTML for SPA routes instead of Bun error page
+  - When accessing client-side routes (like /qsos) via curl or non-JS clients,
+    the server attempted to open them as static files, causing Bun to throw
+    an unhandled ENOENT error that showed an ugly error page
+  - Now checks if a path has a file extension before attempting to serve it
+  - Paths without extensions are immediately served index.html for SPA routing
+  - Also improves the 503 error page with user-friendly HTML when frontend build is missing
+- `223461f`: fix: enable debug logging and improve DCL sync observability
 - `27d2ef1`: fix: preserve DOK data when DCL doesn't send values
   - DCL sync only updates DOK/grid fields when DCL provides non-empty values
   - Prevents accidentally clearing DOK data from manual entry or other sources