Add #rss command family with LLM tags and summaries (v0.20.0)

#rss subcommands on the command channel: help / add <url> <name> /
remove <name> / tags / sources / get <name|#tag>. Sources are stored in
a new rss_sources table in the existing MESH_DB_PATH file (second
node:sqlite connection, case-insensitive names); feeds parsed with
fast-xml-parser (RSS 2.0 + Atom); AI tags and headline summaries via
injected LlmService.chat() with bounded maxTokens (50/200).

CommandService gains prefix registration so one handler owns the whole
#rss family while #ping stays an exact match; wired in CommandModule's
factory — still no constructor-level cycle, no forwardRef. One dead feed
does not sink a tag summary.

src/app.module.ts

@@ -3,6 +3,7 @@ import { BatteryAlertModule } from './battery/battery.module.js';
 import { CommandModule } from './commands/command.module.js';
 import { LlmModule } from './llm/llm.module.js';
 import { MeshModule } from './mesh/mesh.module.js';
+import { RssModule } from './rss/rss.module.js';
 import { WeatherModule } from './weather/weather.module.js';
 
 @Module({
@@ -12,6 +13,7 @@ import { WeatherModule } from './weather/weather.module.js';
     BatteryAlertModule,
     CommandModule,
     LlmModule,
+    RssModule,
   ],
 })
 export class AppModule {}