Align with Twelve Data API docs and add Telegram command menu

data_provider:
- Switch to Authorization header (recommended over apikey query param)
- Enforce 800 credits/day daily limit with warning at 80%
- Fall back to synthetic data when daily limit is reached
- Fix null OHLC field handling (API can return null for any field)

telegram_bot:
- Register commands with set_my_commands so Telegram shows / menu
- Add /credits command to show daily API credit usage and limits

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

telegram_bot.py

@@ -27,7 +27,7 @@ from concurrent.futures import ThreadPoolExecutor
 from datetime import datetime, timezone
 from typing import Dict, Optional
 
-from telegram import Update
+from telegram import BotCommand, Update
 from telegram.constants import ParseMode
 from telegram.ext import Application, CallbackContext, CommandHandler, ContextTypes
 
@@ -514,6 +514,29 @@ class ForexTelegramBot:
             job.schedule_removal()
         await update.message.reply_text("❌ Watch alerts disabled.")
 
+    async def cmd_credits(self, update: Update, context: ContextTypes.DEFAULT_TYPE):
+        """Show API credit usage against the free-tier daily limit."""
+        from data_provider import ForexDataProvider
+        config = self._build_config(self._state(update.effective_chat.id))
+        provider = ForexDataProvider(config)
+        used = provider._daily_credits
+        limit = provider.DAILY_LIMIT
+        remaining = limit - used
+        pct = (used / limit) * 100 if limit else 0
+        bar_filled = int(pct / 5)
+        bar = "█" * bar_filled + "░" * (20 - bar_filled)
+        status = "🟢" if pct < 60 else ("🟡" if pct < 80 else "🔴")
+        text = (
+            "<b>📊 API Credit Usage</b>\n\n"
+            f"<code>{bar}</code> {status}\n"
+            f"<b>Used:</b>      {used} / {limit} credits\n"
+            f"<b>Remaining:</b> {remaining} credits\n\n"
+            "<i>Free tier: 8 credits/min, 800 credits/day\n"
+            "Each full scan uses ~21 credits (7 pairs × 3 timeframes)\n"
+            "≈ 38 scans available per day</i>"
+        )
+        await update.message.reply_text(text, parse_mode=ParseMode.HTML)
+
     # ── Watch job ──────────────────────────────────────────────────
 
     async def _watch_job(self, context: CallbackContext):
@@ -548,9 +571,25 @@ class ForexTelegramBot:
                 "  export TELEGRAM_BOT_TOKEN='your_token_here'"
             )
 
+        async def _register_commands(app: Application) -> None:
+            """Register commands with Telegram so they appear in the / menu."""
+            await app.bot.set_my_commands([
+                BotCommand("scan",    "Scan all major pairs"),
+                BotCommand("signals", "Actionable signals only (grade B+)"),
+                BotCommand("pair",    "Detailed pair analysis — /pair EURUSD"),
+                BotCommand("all",     "Scan major + cross pairs"),
+                BotCommand("tf",      "Set timeframe — /tf H4"),
+                BotCommand("watch",   "Enable periodic alerts"),
+                BotCommand("unwatch", "Disable alerts"),
+                BotCommand("credits", "View API credit usage"),
+                BotCommand("status",  "View current settings"),
+                BotCommand("help",    "Full command reference"),
+            ])
+
         app = (
             Application.builder()
             .token(token)
+            .post_init(_register_commands)
             .build()
         )
 
@@ -564,6 +603,7 @@ class ForexTelegramBot:
         app.add_handler(CommandHandler("all",     self.cmd_all))
         app.add_handler(CommandHandler("watch",   self.cmd_watch))
         app.add_handler(CommandHandler("unwatch", self.cmd_unwatch))
+        app.add_handler(CommandHandler("credits", self.cmd_credits))
 
         return app