fix(observer): pass RequestContext through vikingdb observer for tenant-scoped vector count

[qin-ctx]

Description

The VikingDB observer and /api/v1/observer/vikingdb endpoint always returned vector_count: 0 for non-default tenants. The root cause is that VikingDBObserver.count() was called without RequestContext, falling back to account_id="default" which filters out vectors belonging to other tenants.

This PR threads RequestContext from the HTTP router all the way through ObserverService → VikingDBObserver → VikingVectorIndexBackend.count(ctx=ctx), so each tenant only sees their own vector count.

Related Issue

Fixes #786

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• vikingdb_observer.py — Add ctx: Optional[RequestContext] parameter to get_status_table_async(), get_status_table(), and _get_collection_statuses(). Pass ctx to vikingdb_manager.count(ctx=ctx).
• debug_service.py — Change vikingdb and system from @property to methods accepting ctx parameter. Update is_healthy() to call system().
• observer.py — Pass ctx from router to ObserverService.vikingdb(ctx=ctx) and ObserverService.system(ctx=ctx) for /vikingdb and /system endpoints.
• local.py — Adapt get_status() to call system() as a method.
• tests/ — Update test_debug_service.py and test_vikingdb_observer.py to use method calls instead of property access.
• docs/ — Update SDK examples in docs/zh/api/07-system.md, docs/en/api/07-system.md, and openviking/storage/observers/README.md to reflect the property-to-method change.

Testing

• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Additional Notes

Breaking change for local SDK users: client.observer.vikingdb and client.observer.system are now methods instead of properties. Users need to add parentheses: client.observer.vikingdb(), client.observer.system(). The HTTP SDK client (_HTTPObserver) is not affected as it has its own independent property-based interface.

This is an alternative approach to PR #802, which used include_all_accounts=True to bypass tenant isolation. That approach has two issues:

1. It violates multi-tenant isolation by exposing all tenants' vector counts
2. It has a runtime bug — _SingleAccountBackend.get_collection_info() calls self.count(include_all_accounts=True) but _SingleAccountBackend.count() doesn't accept that parameter, causing a TypeError

Credit-To: jackjin1997

🤖 Generated with Claude Code

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