fix: warn when --lan and --wildcard are used together

[octo-patch]

Fixes #215

Problem

--lan mode uses mDNS (.local domains) to make services accessible to other devices on the local network. However, mDNS does not support wildcard records — only explicitly registered route hostnames are resolvable on other devices.

When a user passes both --lan and --wildcard to portless proxy start, the wildcard subdomain fallback silently has no effect for LAN clients (other devices can't resolve the wildcard subdomains via mDNS). There was no indication of this limitation.

Solution

• Added a runtime warning when both --lan and --wildcard are used together:

  Warning: --wildcard has no effect in LAN mode. mDNS does not support wildcard records,
  so only explicitly registered routes resolve on other devices.
  

• Updated the --wildcard flag description in the run command help to note "(local only, not LAN)"
• Updated PORTLESS_WILDCARD env var description similarly
• Updated the proxy start help to note LAN mode incompatibility with --wildcard
• Added a test for the warning

Testing

Added a new test warns when --lan and --wildcard are both provided following the same pattern as the existing warns when --lan and --tld are both provided test. All 402 tests pass.

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