feat: add HTTP 304 conditional request support for RSS feeds

[lcomplete]

Summary

• Implement HTTP 304 Not Modified support for RSS feed fetching using ETag and Last-Modified headers
• Store HTTP cache headers (ETag, Last-Modified) in Connector entity for conditional requests
• Skip feed processing entirely when server returns 304, reducing unnecessary work and bandwidth
• Update batch organize button to always display item count for clarity

Test plan

• Verify RSS feeds still fetch correctly on first request
• Confirm subsequent fetches send If-None-Match and If-Modified-Since headers
• Validate that 304 responses skip feed processing
• Check that cache headers are properly stored and retrieved from database
• Test batch organize button shows correct count text

🤖 Generated with Claude Code

[augmentcode]

🤖 Augment PR Summary

Summary: This PR adds conditional HTTP caching for RSS connector fetches so unchanged feeds can be skipped via 304 Not Modified, and updates the batch organize UI to always show counts.

Changes:

• Persist RSS HTTP cache metadata (ETag, Last-Modified) on the Connector entity and expose it via ConnectorProperties.
• Add result wrappers (FeedFetchResult, FetchPagesResult) to carry both fetched content and cache header state.
• Implement FeedUtils.fetchFeed(...) using If-None-Match/If-Modified-Since and short-circuit on HTTP 304.
• Extend InfoConnector with a cache-aware fetchNewestPagesWithCache() (defaulting to existing behavior).
• Update RSSConnector to use conditional requests and return cache headers alongside pages.
• Update ConnectorFetchService to skip RSS processing entirely when the feed is not modified, and to store updated cache headers.
• UI: Adjust the batch organize action button to always display the item count for clarity.

Technical Notes: Uses OkHttp response headers (ETag, Last-Modified) for persistence and sends them back on subsequent requests as conditional headers.

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[augmentcode]

Review completed. 1 suggestions posted.

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[augmentcode]

In fetchPages, the “first fetch” path for RSS goes through fetchAllPages()/fetchNewestPages() and never persists httpEtag/httpLastModified, so conditional headers won’t be sent until a later run. Consider capturing/updating cache headers on the initial successful RSS fetch too so the very next poll can benefit from 304 responses.

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