Add GIPHY image search feature

TODO.md

@@ -268,6 +268,22 @@
   - backend debug broadcasts
 
 ## Recent Change Log
+- Date: `2026-03-24`
+- What changed:
+  - Replaced the earlier frontend-only image prototype with an integrated GIPHY image/GIF search flow.
+  - Added backend GIPHY search aggregation with dedupe, up to `100` results, secure download handling, and Gemini-driven multilingual image query expansion into exactly `5` English queries.
+  - Reused the existing result modal for enlarged GIPHY preview and download actions, and added an internal-scroll image results panel with visible `Powered by GIPHY` attribution.
+  - Updated startup config and Unraid template fields for `GIPHY_ENABLED`, `GIPHY_API_KEY`, `GIPHY_MAX_RESULTS`, `GIPHY_RATING`, `GIPHY_LANG`, `GIPHY_DOWNLOAD_DIR`, and `GEMINI_MODEL`.
+  - Added backend tests covering Gemini image-expansion parsing/fallback, GIPHY aggregation/cap behavior, download validation, and handler-level API paths.
+- Why it changed:
+  - The app needed a production-usable image/GIF provider added incrementally without breaking the existing video search experience.
+- How it was verified:
+  - `node --check frontend/app.js`
+  - static code review of backend/frontend wiring and new test coverage
+- What is still risky or incomplete:
+  - This environment currently does not expose `go` or `gofmt`, so Go formatting and `go test ./...` could not be rerun locally in this turn even though new tests were added.
+  - Live browser QA and real GIPHY credential validation still need to be performed in a runtime environment with working API keys.
+
 - Date: `2026-03-24`
 - What changed:
   - Added a working-rule note that git push authentication for this repository should be retried with the local credential file `.local/git-credentials.psd1` before leaving work in a local-only state.
@@ -460,6 +476,13 @@
 - `SEARXNG_GOOGLE_VIDEO_ENGINE`
 - `SEARXNG_WEB_ENGINE`
 - `GEMINI_API_KEY`
+- `GEMINI_MODEL`
+- `GIPHY_ENABLED`
+- `GIPHY_API_KEY`
+- `GIPHY_MAX_RESULTS`
+- `GIPHY_RATING`
+- `GIPHY_LANG`
+- `GIPHY_DOWNLOAD_DIR`
 
 ## Local Development Environment Notes
 - This machine started without `go`, `pip`, `ffmpeg`, `yt-dlp`, or `node`.