feat(claude-code): add web_app variable to disable the web app

[blinkagent]

Adds a web_app variable (default: true) to both the claude-code and agentapi modules. When set to false, AgentAPI still runs but the web UI app icon is not shown in the Coder dashboard.

This mirrors the existing cli_app toggle pattern.

Changes

agentapi module

• New web_app variable (bool, default true)
• coder_app.agentapi_web now has count = var.web_app ? 1 : 0
• task_app_id output returns "" when web_app is false

claude-code module

• New web_app variable (bool, default true) — added for future use
• TODO comment to wire web_app through to agentapi once the agentapi module is published with this support

Usage (once fully wired)

module "claude-code" {
  source  = "registry.coder.com/coder/claude-code/coder"
  ...
  web_app = false  # hides the Claude Code web UI from the dashboard
}

Warning: The web app is required for Coder Tasks (coder_ai_task). Do not disable this if your template uses coder_ai_task — the task_app_id output will be empty and the Tasks UI will not function.

Merge strategy

This needs to land in two steps:

1. Merge this PR — publishes the agentapi module with web_app support, and adds the web_app variable to claude-code (not yet wired through)
2. Follow-up PR — bump the agentapi version in claude-code and replace the TODO with web_app = var.web_app