refactor: merge BOT_TOKEN + ADDITIONAL_BOT_TOKENS into single BOT_TOKENS env + speed audit

BOT_TOKENS env:
- Single BOT_TOKENS env var (comma-separated) replaces BOT_TOKEN + ADDITIONAL_BOT_TOKENS
- Backward compat: falls back to BOT_TOKEN + ADDITIONAL_BOT_TOKENS if BOT_TOKENS unset
- Config exposes botTokens: string[] instead of botToken + additionalBotTokens
- Updated env.ts, bot-pool.ts, docker-compose.yml, .env.example, CLAUDE.md, all tests

Speed audit (S3 -> Telegram upload flow):
- Hoisted 5 dynamic await import('../../../db/index') to top-level static imports
  in s3-controller.ts (3x) and web-api-controller.ts (2x)
  -> saves module resolution + async overhead on every upload
- Removed stale UPLOAD_CONCURRENCY env from docker-compose.yml
  (already removed from env.ts in prior refactor)

Upload flow is already concurrent:
- streamBodyToTemp() uses Bun.file(path).writer() — O(1) memory, safe for multi-GB blobs
- utils/chunked-storage.ts reads chunks serially but uploads concurrently with
  inFlight backpressure at effectiveConcurrency * 2 (= 16 with 8 bots)
- bot-pool.ts: per-bot PQueue(concurrency=1), 8 bots = 8 concurrent uploads per file,
  selectBot() picks least-loaded, 429 detection + inner+outer retry loops
- TELEGRAM_API_TIMEOUT_MS=120s — ample for 48MB chunks
- Infrastructure chunked-storage.ts (DI-based, dead code) has serial upload trap —
  noted for future cleanup

src/env.ts

@@ -1,8 +1,8 @@
 import logger from './utils/logger';
 
 interface AppConfig {
-  botToken: string;
-  additionalBotTokens: string[];
+  /** All bot tokens merged from BOT_TOKENS (or BOT_TOKEN + ADDITIONAL_BOT_TOKENS fallback) */
+  botTokens: string[];
   storageChatId: number;
   baseUrl: string;
   databaseUrl: string;
@@ -28,8 +28,21 @@ interface AppConfig {
   s3VhostDomains: string[];
 }
 
+// Validate bot tokens: BOT_TOKENS (new) or fallback to BOT_TOKEN + ADDITIONAL_BOT_TOKENS
+const botTokensRaw =
+  process.env.BOT_TOKENS ||
+  [process.env.BOT_TOKEN, process.env.ADDITIONAL_BOT_TOKENS].filter(Boolean).join(',');
+
+if (!botTokensRaw) {
+  logger.error(
+    'Missing required environment variables: BOT_TOKENS (or BOT_TOKEN + ADDITIONAL_BOT_TOKENS)',
+  );
+  throw new Error(
+    'Missing environment variables: BOT_TOKENS (or BOT_TOKEN + ADDITIONAL_BOT_TOKENS)',
+  );
+}
+
 const requiredEnv = {
-  BOT_TOKEN: process.env.BOT_TOKEN,
   STORAGE_CHANNEL_ID: process.env.STORAGE_CHANNEL_ID,
   BASE_URL: process.env.BASE_URL,
   DATABASE_URL: process.env.DATABASE_URL,
@@ -93,8 +106,7 @@ const maskDatabaseUrl = (value: string): string =>
   value.replace(/:\/\/([^:]+):([^@]+)@/, '://$1:***@');
 
 export const config: AppConfig = {
-  botToken: process.env.BOT_TOKEN!,
-  additionalBotTokens: parseTokens(process.env.ADDITIONAL_BOT_TOKENS),
+  botTokens: parseTokens(botTokensRaw),
   storageChatId: parseInt(process.env.STORAGE_CHANNEL_ID!, 10),
   baseUrl: process.env.BASE_URL!,
   databaseUrl: process.env.DATABASE_URL!,
@@ -126,8 +138,7 @@ export const config: AppConfig = {
 logger.info('Environment variables loaded', {
   config: {
     ...config,
-    botToken: maskSecret(config.botToken),
-    additionalBotTokens: config.additionalBotTokens.map(maskSecret),
+    botTokens: config.botTokens.map(maskSecret),
     databaseUrl: maskDatabaseUrl(config.databaseUrl),
     adminApiToken: maskSecret(config.adminApiToken),
     adminApiTokenEnabled: config.adminApiToken.length > 0,

src/infrastructure/telegram/bot-pool.ts

@@ -64,7 +64,7 @@ export class BotPool implements ITelegramService {
   private readonly bots: BotEntry[] = [];
 
   constructor() {
-    const tokens = Array.from(new Set([config.botToken, ...config.additionalBotTokens]));
+    const tokens = Array.from(new Set(config.botTokens));
     this.bots = tokens.map((token, index) => ({
       index,
       token,

src/interfaces/http/controllers/s3-controller.ts

@@ -8,6 +8,7 @@ import {
   listObjectsByPrefix,
   softDeleteFile,
 } from '../../../db/files-ext';
+import { db, files as fileSchema } from '../../../db/index';
 import {
   abortMultipartUpload,
   completeMultipartUpload,
@@ -1082,7 +1083,6 @@ const storeFileFromTemp = async (
   fileStream.destroy();
 
   const publicId = nanoid();
-  const { db, files: fileSchema } = await import('../../../db/index');
 
   await db.insert(fileSchema).values({
     publicId,
@@ -1194,7 +1194,6 @@ const handleCopyObject = async (
   }
 
   const publicId = nanoid();
-  const { db, files: fileSchema } = await import('../../../db/index');
 
   await db.insert(fileSchema).values({
     publicId,
@@ -1679,7 +1678,6 @@ const handleCompleteMultipartUpload = async (
   const combinedEtag = storedParts.map((p) => p.etag).join('-');
 
   const publicId = nanoid();
-  const { db, files: fileSchema } = await import('../../../db/index');
 
   // M7: Use stored content-type from the multipart record if available
   const mimeType = multipart.contentType || 'application/octet-stream';

src/interfaces/http/controllers/web-api-controller.ts

@@ -8,6 +8,7 @@ import {
   listObjectsByPrefix,
   softDeleteFile,
 } from '../../../db/files-ext';
+import { db, files as fileSchema } from '../../../db/index';
 import { botPool } from '../../../infrastructure/telegram/bot-pool';
 import logger from '../../../shared/logger/index';
 import { cleanupTempFile, ensureExtension, getErrorMessage } from '../../../shared/utils/file';
@@ -246,7 +247,6 @@ export const handleUploadObjectV1 = async (
   );
 
   const publicId = nanoid();
-  const { db, files: fileSchema } = await import('../../../db/index');
 
   await db.insert(fileSchema).values({
     publicId,
@@ -361,7 +361,6 @@ export const handleCopyObjectV1 = async (req: Request, params: RouteParams): Pro
   }
 
   const publicId = nanoid();
-  const { db, files: fileSchema } = await import('../../../db/index');
 
   await db.insert(fileSchema).values({
     publicId,