feat: integrate Google Scholar alerts and improve paper filtering pipeline

- Add Google Scholar Alert collection via Gmail IMAP
- Add Gmail App Password based authentication
- Add Google Scholar environment variables to NAS compose configuration
- Enable Google Scholar Alert source in config.nas.yaml
- Disable subject filtering that incorrectly excluded Scholar alert emails
- Parse paper titles and links from Google Scholar alert HTML emails
- Deduplicate collected Scholar papers by normalized title
- Filter Scholar UI/control links such as update alert and unsubscribe entries
- Filter bracket-only alert labels such as [automotive radar]

- Add Google Scholar specific relevance threshold
- Keep global min_relevance at 2
- Set Google Scholar minimum relevance to 3
- Reduce Scholar candidates from 229 collected / 207 merged to 28 accepted

- Add Gemini API rate limiting
- Enforce minimum 13 second interval between Gemini requests
- Apply shared rate limiter to abstract and full-text enrichment
- Prevent Gemini free-tier 5 RPM quota errors
- Verify retry processing of previously failed AI enrichment jobs

- Verify end-to-end NAS workflow
- Google Scholar Alert collection successful
- Gemini enrichment successful without HTTP 429 errors
- Joplin report generation and WebDAV synchronization successful

src/paper_monitor/oa_resolver.py

@@ -34,7 +34,11 @@ class UnpaywallResolver:
             response.raise_for_status()
 
         except requests.exceptions.HTTPError as exc:
-            status = exc.response.status_code if exc.response else None
+            status = (
+                exc.response.status_code
+                if exc.response is not None
+                else None
+            )
 
             # DOI not present in Unpaywall is not fatal.
             if status == 404: