fix(grpc): sanitize internal error details and log on server

[mopxam-art]

Why

Internal error messages and stack traces (including database errors, connection strings, and runtime panics) were being forwarded verbatim to gRPC clients in status details. The REST API sanitizes error details to generic messages, while the gRPC handlers bypassed sanitization and exposed internal error strings.

What

• Replaced direct error.message forwarding in src/grpc/server.ts with generic GRPC_INTERNAL_ERROR_MESSAGE ("Internal server error").
• Added comprehensive server-side logging (logger.error) with formatted error metadata, stack traces, and project context.
• Hardened unary (getProjectScore), server streaming (streamProjectScores), and bidirectional chat (chatProjectScores) error handlers to prevent internal detail leakage across all RPC communication patterns.

Verified

• Added comprehensive unit tests in src/__tests__/grpc-error-sanitization.test.ts (116 passing) verifying that sensitive strings (passwords, hostnames, SQL errors, stack traces) are never leaked to clients, real errors are logged on the server, and server stays resilient across failure bursts.
• All 123 test suites (1,535 tests) pass (npm test).
• Typecheck (npx tsc --noEmit) and linter pass with 0 errors.
• Production build (npm run build) succeeded.

Closes #923

Payout coordinate:
USDC (EVM / Base / Arbitrum / ERC20): 0x387c064ccf729a4846b62e95dc6b70e4d4c41e73