refactor: comprehensive codebase cleanup and architecture hardening

- Sprint 1 (Quick Wins): Remove dead analytics modules, fix 4 unresolved
  imports, replace 3 console.warn with logger, remove mock-crc import
- Sprint 2 (Architecture): Create MascotChatRepository, AnalysisRepository,
  3 Zod schemas (mascot-chat, analysis, voice), deduplicate error classes,
  move 3 SQL queries from routes to repository
- Sprint 3 (Complexity): Replace 7 any types with proper interfaces,
  extract 6 helpers from prepareMediaMessage (CC 85 -> ~15)
- Sprint 4 (Config): Remove 22 dead env vars from .env, add 30 missing
  vars to .env.example, standardize naming

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/discord-gateway/src/shared/config/config.ts

@@ -1,6 +1,6 @@
 import "dotenv/config";
+import { ConfigError } from "@bete/shared/errors";
 import { z } from "zod";
-import { ConfigError } from "../errors/errors.js";
 
 const configSchema = z
   .object({

services/discord-gateway/src/shared/errors/errors.ts

@@ -1,50 +0,0 @@
-export class AppError extends Error {
-  public code: string;
-  public statusCode: number;
-
-  constructor(message: string, code: string, statusCode: number = 500) {
-    super(message);
-    this.code = code;
-    this.statusCode = statusCode;
-    this.name = "AppError";
-    Error.captureStackTrace(this, this.constructor);
-  }
-}
-
-export class ConfigError extends AppError {
-  constructor(message: string) {
-    super(message, "CONFIG_ERROR", 500);
-    this.name = "ConfigError";
-  }
-}
-
-export class AudioError extends AppError {
-  constructor(message: string) {
-    super(message, "AUDIO_ERROR", 500);
-    this.name = "AudioError";
-  }
-}
-
-export class DatabaseError extends AppError {
-  constructor(message: string) {
-    super(message, "DATABASE_ERROR", 500);
-    this.name = "DatabaseError";
-  }
-}
-
-export class VoiceConnectionError extends AppError {
-  constructor(message: string) {
-    super(message, "VOICE_CONNECTION_ERROR", 500);
-    this.name = "VoiceConnectionError";
-  }
-}
-
-export class ValidationError extends AppError {
-  public details?: Record<string, string[]>;
-
-  constructor(message: string, details?: Record<string, string[]>) {
-    super(message, "VALIDATION_ERROR", 400);
-    this.details = details;
-    this.name = "ValidationError";
-  }
-}