feat(bots): bot framework polish + store

- /ws/bot endpoint: bot token auth via query param, SHA-256 lookup
- Bot WS actions: SEND_MESSAGE + DELETE_MESSAGE handled in gateway
- Bot messages: bot_id on messages table, bot badge in chat (green + BOT tag)
- Bot store: /bots lists all bots with server count + add-to-server
- Bot manager moved to /bots/manage
- Fix: command routes were double-nested under /bots/{botID}/commands
- Fix: fetchServerCommands route corrected to /bots/servers/...

internal/db/db.go

@@ -565,5 +565,9 @@ CREATE TABLE IF NOT EXISTS feature_request_votes (
 	PRIMARY KEY (feature_request_id, user_id)
 );
 CREATE INDEX IF NOT EXISTS idx_feature_request_votes_fr ON feature_request_votes(feature_request_id);
+
+-- Bot messages: track which bot authored a message
+ALTER TABLE messages ADD COLUMN IF NOT EXISTS bot_id UUID REFERENCES bots(id) ON DELETE SET NULL;
+CREATE INDEX IF NOT EXISTS idx_messages_bot ON messages(bot_id) WHERE bot_id IS NOT NULL;
 `