feat: add web search tool with reranking support

Integrates SearXNG web search as a tool available during chat when the
agent has search enabled. Supports optional reranking of results via a
configurable reranking model. Replaces Python subprocess evaluation with
@pydantic/monty WASM runtime. Introduces stable tool call ID mapping to
avoid exposing provider-native IDs to the database.

app/composables/useModels.ts

@@ -6,6 +6,7 @@ export type Provider = typeof schema.providers.$inferSelect;
 
 export type ProviderWithModels = Provider & {
     models: Model[];
+    defaultBaseUrl?: string;
 };
 
 export type ModelWithProvider = Model & {