feat(ui): dark theme redesign, fix image search and defaults

- Inline CSS in base.html (Inter, dark mode, sticky search, tabs, results)
- Remove HTMX/JS from templates; pagination via GET links
- Atmospheric side gradients + grid; wider column on large viewports
- Parse ?category= for HTML tabs (fixes Images category routing)
- Include bing_images, ddg_images, qwant_images in local_ported defaults
- Default listen port 5355; update Docker, compose, flake, README
- Favicon img uses /favicon/ proxy; preferences without inline JS

Made-with: Cursor

README.md

@@ -110,7 +110,7 @@ go run ./cmd/samsa -config config.toml
 ### Example
 
 ```bash
-curl "http://localhost:8080/search?q=golang&format=json&engines=github,duckduckgo"
+curl "http://localhost:5355/search?q=golang&format=json&engines=github,duckduckgo"
 ```
 
 ### Response (JSON)
@@ -155,7 +155,7 @@ Copy `config.example.toml` to `config.toml` and edit. All settings can also be o
 
 | Variable | Description |
 |---|---|
-| `PORT` | Listen port (default: 8080) |
+| `PORT` | Listen port (default: 5355) |
 | `BASE_URL` | Public URL for OpenSearch XML |
 | `UPSTREAM_SEARXNG_URL` | Upstream instance URL |
 | `LOCAL_PORTED_ENGINES` | Comma-separated local engine list |