fix(slm): add tablename collision check for dual SQLAlchemy bases (#1878)

[mrveiss]

Summary

• Adds _check_tablename_collisions() startup check in SLM main.py
• Detects shared tablenames across both SQLAlchemy Base MetaData objects
• Logs WARNING for overlaps to catch model misplacement bugs early (like Bug: SLM user_mfa FK datatype mismatch prevents clean DB initialization #1854)
• Runs before create_all / migrations so conflicts are caught immediately
• Does not raise since some names are intentionally shared across databases
• Closes tech-debt: SLM has dual SQLAlchemy Base classes — fragile table ownership #1878

Test plan

• SLM starts without errors
• Warning logged if intentionally shared tablenames exist
• No false positives for legitimate separate-database tables

🤖 Generated with Claude Code

[github-actions]

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