feat: integrate SearXNG web search service with platform capabilities

- Added SearXNG service configuration to Docker setup, including environment variables and health checks.
- Introduced new settings management for web search in the frontend, allowing users to enable/disable and configure search engines and language preferences.
- Updated backend to support web search functionality, including database schema changes and service integration.
- Implemented health check endpoint for the web search service and integrated it into the application.
- Removed legacy SearXNG API connector references in favor of the new platform service approach.

docker/searxng/limiter.toml

@@ -0,0 +1,5 @@
+[botdetection.ip_limit]
+link_token = false
+
+[botdetection.ip_lists]
+pass_ip = ["0.0.0.0/0"]

docker/searxng/settings.yml

@@ -0,0 +1,60 @@
+use_default_settings: true
+
+server:
+  secret_key: "override-me-via-env"
+  limiter: false
+  image_proxy: false
+  method: "GET"
+  default_http_headers:
+    X-Robots-Tag: "noindex, nofollow"
+
+search:
+  formats:
+    - html
+    - json
+  default_lang: "auto"
+  autocomplete: ""
+  safe_search: 0
+
+ui:
+  static_use_hash: true
+
+outgoing:
+  request_timeout: 12.0
+  pool_connections: 100
+  pool_maxsize: 20
+  enable_http2: true
+
+engines:
+  - name: google
+    disabled: false
+    weight: 1.2
+  - name: duckduckgo
+    disabled: false
+    weight: 1.1
+  - name: brave
+    disabled: false
+    weight: 1.0
+  - name: qwant
+    disabled: false
+    weight: 0.9
+  - name: mojeek
+    disabled: false
+    weight: 0.7
+  - name: wikipedia
+    disabled: false
+    weight: 0.8
+  - name: wikidata
+    disabled: false
+    weight: 0.6
+  - name: currency_convert
+    disabled: false
+  - name: duckduckgo definitions
+    disabled: false
+  - name: stackoverflow
+    disabled: false
+    weight: 0.7
+  - name: bing
+    disabled: true
+  - name: yahoo
+    disabled: true