refactor: restore behavior the branch had changed (codex review)

A codex review of the branch found seven places where earlier refactor commits changed behavior. Each is restored here with a test:

- base_service imported flood_scope relatively; the local-service loader also runs that file as local_services.base_service, where the import cannot resolve. Now absolute.
- Radio-health fields were initialized after commands and services were built, so a plugin constructor reading is_radio_offline raised. They are now set before any plugin.
- Removing the per-command can_execute overrides made 31 commands honor skip_channel_check, which their overrides had dropped. BaseCommand.honors_skip_channel_check (False on exactly those commands) keeps them enforcing their channel list.
- CommandManager.get_plugin_metadata, WxCommand.get_weather_for_zipcode and PluginLoader.validate_plugin were public compatibility entry points; they are back.
- feed_manager stopped exporting DEFAULT_MAX_FEED_RESPONSE_BYTES and DEFAULT_MAX_PARSED_FEED_ITEMS despite the commit saying it re-exported them; it does now.
- wx and gwx logged companion-location lookup failures at WARNING; the shared helper logged at debug. It now takes the level.
- The INFO 'MESSAGE ROUTING' / 'DIRECT MESSAGE' lines for pubkey-correlated DMs were removed with the dead path_info computation; they are logged again by a log-only helper.

modules/service_plugins/base_service.py

@@ -10,7 +10,9 @@ from abc import ABC, abstractmethod
 from dataclasses import dataclass
 from typing import Any, Optional
 
-from ..flood_scope import section_flood_scope
+# Absolute on purpose: the local-service loader also executes this file as
+# local_services.base_service, where a relative parent import cannot resolve.
+from modules.flood_scope import section_flood_scope
 
 
 @dataclass