refactor: remove legacy SearXNG API references and web search settings

- Deleted the migration script for adding web search columns to the database.
- Removed web search related fields from the SearchSpace model and schemas.
- Eliminated web search health check endpoint and associated service logic.
- Updated frontend components to remove web search settings management.
- Cleaned up references to SearXNG API in various modules, transitioning to a platform service approach.

surfsense_backend/alembic/versions/106_add_platform_web_search.py

@@ -1,51 +0,0 @@
-"""106_add_platform_web_search
-
-Revision ID: 106
-Revises: 105
-Create Date: 2026-03-14
-
-Adds web_search_enabled and web_search_config columns to searchspaces for
-per-space control over the platform web search capability.
-
-Also removes legacy SEARXNG_API connector rows — web search is now a platform
-service, not a per-user connector.
-"""
-
-from __future__ import annotations
-
-from collections.abc import Sequence
-
-import sqlalchemy as sa
-from sqlalchemy.dialects.postgresql import JSONB
-
-from alembic import op
-
-revision: str = "106"
-down_revision: str | None = "105"
-branch_labels: str | Sequence[str] | None = None
-depends_on: str | Sequence[str] | None = None
-
-
-def upgrade() -> None:
-    op.add_column(
-        "searchspaces",
-        sa.Column(
-            "web_search_enabled",
-            sa.Boolean(),
-            nullable=False,
-            server_default=sa.text("true"),
-        ),
-    )
-    op.add_column(
-        "searchspaces",
-        sa.Column("web_search_config", JSONB, nullable=True),
-    )
-
-    op.execute(
-        "DELETE FROM search_source_connectors WHERE connector_type = 'SEARXNG_API'"
-    )
-
-
-def downgrade() -> None:
-    op.drop_column("searchspaces", "web_search_config")
-    op.drop_column("searchspaces", "web_search_enabled")