feat: add ACP agent foundation (synced agents table, proxy, ws-tickets)

backend/.env.example

@@ -90,4 +90,10 @@ RATE_LIMIT_ENABLED=true
 # Controls which proxy headers are trusted for IP extraction in rate limiting.
 # Set to 'cloudflare' to trust CF-Connecting-IP, 'akamai' for True-Client-IP.
 # Leave empty to use the direct socket IP only (all proxy headers are ignored).
-TRUSTED_PROXY=
+TRUSTED_PROXY=
+
+# Agents
+# Comma-separated list of enabled agent IDs. Empty = all enabled. (default: '')
+ENABLED_AGENTS=
+# Allow users to register custom agents with arbitrary URLs. (default: false)
+ALLOW_CUSTOM_AGENTS=false

backend/drizzle/0013_next_ulik.sql

@@ -0,0 +1,28 @@
+CREATE TABLE "powersync"."agents" (
+	"id" text NOT NULL,
+	"name" text,
+	"type" text,
+	"transport" text,
+	"command" text,
+	"args" text,
+	"url" text,
+	"auth_method" text,
+	"icon" text,
+	"is_system" integer DEFAULT 0,
+	"enabled" integer DEFAULT 1,
+	"registry_id" text,
+	"installed_version" text,
+	"registry_version" text,
+	"distribution_type" text,
+	"install_path" text,
+	"package_name" text,
+	"description" text,
+	"default_hash" text,
+	"deleted_at" timestamp,
+	"user_id" text NOT NULL,
+	CONSTRAINT "agents_id_user_id_pk" PRIMARY KEY("id","user_id")
+);
+--> statement-breakpoint
+ALTER TABLE "powersync"."chat_threads" ADD COLUMN "agent_id" text;--> statement-breakpoint
+ALTER TABLE "powersync"."agents" ADD CONSTRAINT "agents_user_id_user_id_fk" FOREIGN KEY ("user_id") REFERENCES "public"."user"("id") ON DELETE cascade ON UPDATE no action;--> statement-breakpoint
+CREATE INDEX "idx_agents_user_id" ON "powersync"."agents" USING btree ("user_id");