Phase 3: PluginWebMixin SDK + web plugin control panels

- New: sdk/plugin_web.py (PluginWebMixin: web pages, API routes, SSE)
- New: services/web_panel/routes/plugin_web.py (3 endpoints)
- New: plugins/example_plugin/dashboard.html (counter + SSE demo)
- Updated: example_plugin uses PluginWebMixin
- Tests: 28/28 passing

plugins/example_plugin/__init__.py

@@ -1,22 +1,28 @@
 #!/usr/bin/env python3
-import logging
+import logging, os
 from typing import Dict
+from aiohttp import web
 try:
     from sdk.plugin_command_decorator import plugin_command, command
+    from sdk.plugin_web import PluginWebMixin
 except ImportError:
     def plugin_command(n=None,d=None,p=None):
-        def deco(f):
-            f._is_plugin_command=True;f._command_name=n or f.__name__
-            f._command_description=d or (f.__doc__ or "").strip();return f
+        def deco(f):f._is_plugin_command=True;f._command_name=n or f.__name__;return f
         return deco
-    command=plugin_command
+    class PluginWebMixin:
+        def register_web_page(self,*a,**k):pass
+        def register_api_route(self,*a,**k):pass
 
 logger=logging.getLogger(__name__)
 
-class Plugin:
-    def __init__(self, plugin_name=None, config=None, bridge=None, n=None, c=None):
-        self.plugin_name=plugin_name or n;self.config=config or c;self.bridge=bridge
-        self.network_bridge=None;self.is_running=False
+class Plugin(PluginWebMixin):
+    def __init__(self, plugin_name=None, config=None, bridge=None):
+        PluginWebMixin.__init__(self)
+        self.plugin_name=plugin_name or "example"
+        self.config=config or {}
+        self.bridge=bridge
+        self.network_bridge=None
+        self.is_running=False
 
     async def initialize(self):
         logger.info(f"init: {self.plugin_name}")
@@ -28,17 +34,21 @@ class Plugin:
                 "/api/example/info",self._api_info,methods=["GET"],require_auth=False)
         except Exception as e:
             logger.warning(f"network skip: {e}")
+        # Load dashboard HTML from file
+        html_path=os.path.join(os.path.dirname(__file__),"dashboard.html")
+        if os.path.exists(html_path):
+            with open(html_path) as hf:
+                self.register_web_page("example_plugin","Example Plugin",hf.read(),icon="P")
         self.is_running=True
 
     async def _api_info(self,req):
-        from aiohttp import web
         return web.json_response({"plugin":self.plugin_name,"status":"running"})
 
     @plugin_command(name="echo",description="echo input")
     async def cmd_echo(self,*args):
         return " ".join(args) if args else "echo: no input"
 
-    @plugin_command(name="plugin_status",description="show plugin status")
+    @plugin_command(name="plugin_status",description="show status")
     async def cmd_status(self,*args):
         return f"{self.plugin_name} v{self.config.get('version','?')} - running"