Fix #895: replace magic number in broker param_count check

[Chessing234]

Summary

• Defined named constants _MIN_BROKER_INIT_PARAMS = 2 and _MIN_BROKER_INIT_PARAMS_WITH_FEED = 3 to replace unexplained magic numbers
• Applied across quotes_service.py, history_service.py, and depth_service.py
• The constants clarify that 2 = self + auth_token, and 3 adds feed_token

Closes #895

Verification

• All modified files pass Python syntax validation
• No behavioral changes — only readability improvement
• Constants are module-level with explanatory comments

Test plan

• Application starts normally
• Broker data handlers initialize correctly (quotes, history, depth)
• No regressions in broker API calls

🤖 Generated with Claude Code

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Summary by cubic

Replace magic numbers in BrokerData.__init__ param-count checks with named constants for clearer intent; no behavior change. Fixes #895.

• Refactors
  • Added _MIN_BROKER_INIT_PARAMS = 2 (self + auth_token) in quotes_service.py and history_service.py.
  • In depth_service.py, also added _MIN_BROKER_INIT_PARAMS_WITH_FEED = 3 (adds feed_token).
  • Updated conditional checks to use these constants when creating BrokerData (auth only, auth+feed, auth+feed+user_id).
  • Added brief comments explaining the parameter mapping.

^{Written for commit 347aefa. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 3 files