chore: remove unused tailnet v1 tables and queries (#21646)

Removes the legacy tailnet v1 API tables (`tailnet_clients`, `tailnet_agents`, `tailnet_client_subscriptions`) and their associated queries, triggers, and functions. These were superseded by the v2 tables (`tailnet_peers`, `tailnet_tunnels`) in migration 000168, and the v1 API code was removed in commit d6154c4310, but the database artifacts were never cleaned up.

**Changes:**
- New migration `000410_remove_tailnet_v1_tables` to drop the unused tables
- Removed 11 unused queries from `tailnet.sql`
- Removed associated manual wrapper methods in `dbauthz` and `dbmetrics`
- ~930 lines deleted across 11 files

coderd/database/migrations/000410_remove_tailnet_v1_tables.down.sql

@@ -0,0 +1,124 @@
+-- Restore tailnet v1 API tables (unused, but required for rollback).
+
+-- Create tables.
+CREATE TABLE tailnet_clients (
+    id uuid NOT NULL,
+    coordinator_id uuid NOT NULL,
+    updated_at timestamp with time zone NOT NULL,
+    node jsonb NOT NULL,
+    PRIMARY KEY (id, coordinator_id),
+    FOREIGN KEY (coordinator_id) REFERENCES tailnet_coordinators (id) ON DELETE CASCADE
+);
+
+CREATE TABLE tailnet_agents (
+    id uuid NOT NULL,
+    coordinator_id uuid NOT NULL,
+    updated_at timestamp with time zone NOT NULL,
+    node jsonb NOT NULL,
+    PRIMARY KEY (id, coordinator_id),
+    FOREIGN KEY (coordinator_id) REFERENCES tailnet_coordinators (id) ON DELETE CASCADE
+);
+
+CREATE TABLE tailnet_client_subscriptions (
+    client_id uuid NOT NULL,
+    coordinator_id uuid NOT NULL,
+    agent_id uuid NOT NULL,
+    updated_at timestamp with time zone NOT NULL,
+    PRIMARY KEY (client_id, coordinator_id, agent_id),
+    FOREIGN KEY (coordinator_id) REFERENCES tailnet_coordinators (id) ON DELETE CASCADE
+);
+
+-- Create indexes.
+CREATE INDEX idx_tailnet_agents_coordinator ON tailnet_agents USING btree (coordinator_id);
+CREATE INDEX idx_tailnet_clients_coordinator ON tailnet_clients USING btree (coordinator_id);
+
+-- Create trigger functions.
+CREATE FUNCTION tailnet_notify_agent_change() RETURNS trigger
+    LANGUAGE plpgsql
+    AS $$
+BEGIN
+	IF (OLD IS NOT NULL) THEN
+		PERFORM pg_notify('tailnet_agent_update', OLD.id::text);
+		RETURN NULL;
+	END IF;
+	IF (NEW IS NOT NULL) THEN
+		PERFORM pg_notify('tailnet_agent_update', NEW.id::text);
+		RETURN NULL;
+	END IF;
+END;
+$$;
+
+CREATE FUNCTION tailnet_notify_client_change() RETURNS trigger
+    LANGUAGE plpgsql
+    AS $$
+DECLARE
+	var_client_id uuid;
+	var_coordinator_id uuid;
+	var_agent_ids uuid[];
+	var_agent_id uuid;
+BEGIN
+	IF (NEW.id IS NOT NULL) THEN
+		var_client_id = NEW.id;
+		var_coordinator_id = NEW.coordinator_id;
+	ELSIF (OLD.id IS NOT NULL) THEN
+		var_client_id = OLD.id;
+		var_coordinator_id = OLD.coordinator_id;
+	END IF;
+
+	-- Read all agents the client is subscribed to, so we can notify them.
+	SELECT
+		array_agg(agent_id)
+	INTO
+		var_agent_ids
+	FROM
+		tailnet_client_subscriptions subs
+	WHERE
+		subs.client_id = NEW.id AND
+		subs.coordinator_id = NEW.coordinator_id;
+
+	-- No agents to notify
+	if (var_agent_ids IS NULL) THEN
+		return NULL;
+	END IF;
+
+	-- pg_notify is limited to 8k bytes, which is approximately 221 UUIDs.
+	-- Instead of sending all agent ids in a single update, send one for each
+	-- agent id to prevent overflow.
+	FOREACH var_agent_id IN ARRAY var_agent_ids
+	LOOP
+		PERFORM pg_notify('tailnet_client_update', var_client_id || ',' || var_agent_id);
+	END LOOP;
+
+	return NULL;
+END;
+$$;
+
+CREATE FUNCTION tailnet_notify_client_subscription_change() RETURNS trigger
+    LANGUAGE plpgsql
+    AS $$
+BEGIN
+	IF (NEW IS NOT NULL) THEN
+		PERFORM pg_notify('tailnet_client_update', NEW.client_id || ',' || NEW.agent_id);
+		RETURN NULL;
+	ELSIF (OLD IS NOT NULL) THEN
+		PERFORM pg_notify('tailnet_client_update', OLD.client_id || ',' || OLD.agent_id);
+		RETURN NULL;
+	END IF;
+END;
+$$;
+
+-- Create triggers.
+CREATE TRIGGER tailnet_notify_agent_change
+    AFTER INSERT OR DELETE OR UPDATE ON tailnet_agents
+    FOR EACH ROW
+    EXECUTE FUNCTION tailnet_notify_agent_change();
+
+CREATE TRIGGER tailnet_notify_client_change
+    AFTER INSERT OR DELETE OR UPDATE ON tailnet_clients
+    FOR EACH ROW
+    EXECUTE FUNCTION tailnet_notify_client_change();
+
+CREATE TRIGGER tailnet_notify_client_subscription_change
+    AFTER INSERT OR DELETE OR UPDATE ON tailnet_client_subscriptions
+    FOR EACH ROW
+    EXECUTE FUNCTION tailnet_notify_client_subscription_change();

coderd/database/migrations/000410_remove_tailnet_v1_tables.up.sql

@@ -0,0 +1,20 @@
+-- Remove unused tailnet v1 API tables.
+-- These tables were superseded by tailnet_peers and tailnet_tunnels in migration
+-- 000168. The v1 API code was removed in commit d6154c4310 ("remove tailnet v1
+-- API support"), but the tables and queries were never cleaned up.
+
+-- Drop triggers first (they reference the functions).
+DROP TRIGGER IF EXISTS tailnet_notify_agent_change ON tailnet_agents;
+DROP TRIGGER IF EXISTS tailnet_notify_client_change ON tailnet_clients;
+DROP TRIGGER IF EXISTS tailnet_notify_client_subscription_change ON tailnet_client_subscriptions;
+
+-- Drop the trigger functions.
+DROP FUNCTION IF EXISTS tailnet_notify_agent_change();
+DROP FUNCTION IF EXISTS tailnet_notify_client_change();
+DROP FUNCTION IF EXISTS tailnet_notify_client_subscription_change();
+
+-- Drop the tables. Foreign keys and indexes are dropped automatically via CASCADE.
+-- Order matters due to potential foreign key relationships.
+DROP TABLE IF EXISTS tailnet_client_subscriptions;
+DROP TABLE IF EXISTS tailnet_agents;
+DROP TABLE IF EXISTS tailnet_clients;