feat: add optional hosted-TickerAll data/execution provider

[miguelangelo78]

Summary

Adds an optional TickerAll provider so QuantumTerminal can run without a local MetaTrader 5 terminal.

The problem

Right now QuantumTerminal needs the MT5 terminal running locally for data and trades. That ties it to a Windows machine with the terminal open, and the MT5 Python API isn't thread-safe, so under load it can crash or return bad data (issue #1).
This provider is an alternative path that avoids those constraints.

The Solution: TickerAll

https://tickerall.com

TickerAll is a hosted API for accessing MT5 and MT4 accounts: you give it a broker login and it lets you connect to your MT5 broker without having to run MT5 locally. It returns ticks, candles, positions, account info, and order execution over REST and WebSocket, with no MT5 terminal involved.

Problems it solves:

• No more MT5 running on your machine
• Not locked to Windows - can run on any OS
• You can run multiple MT5 accounts effortlessly - it's scalable
• Since the MetaTrader5 Python package isn't loaded with this provider, the thread-safety problem in Fix MT5 thread-safety issues in data_server.py #1 can't happen anymore.
• Real time data: ticks and position updates also arrive live over one WebSocket, so there's no extra polling delay.

You can still run the original MT5 logic, just need to unset the env var TICKERALL_API_KEY.

Trying it

git checkout feat/tickerall-provider
pip install -r backend/requirements.txt

export TICKERALL_API_KEY=your_key          # key from tickerall.com
export TICKERALL_SERVER=Exness-MT5Trial7   # your broker server
export TICKERALL_ACCOUNT=12345678          # your broker login
export TICKERALL_PASSWORD=your_password    # your broker password

You will need to get a TICKERALL_API_KEY, which is free!

Then start QuantumTerminal the usual way.

To go back to MT5, unset TICKERALL_API_KEY.

What changed

A new provider in backend/providers/, small hooks so the existing account/positions/status routes can use it, and an optional dependency in requirements.txt. Docs and tests are included.