Unify backend logging, add context keys, and capture uncaught exceptions

[AJaySi]

Motivation

• Ensure all runtime errors (sync and async) are captured and logged with full tracebacks to improve observability and post-mortem debugging.
• Provide a consistent, minimally-verbose default logging output while allowing verbose developer mode to show full diagnostics.
• Route Uvicorn logs into the same sinks/format so startup/server logs match application logs and respect the chosen verbosity.

Description

• Added global uncaught exception handling by registering sys.excepthook and an asyncio loop exception handler to surface unhandled exceptions with tracebacks via Loguru in backend/logging_config.py.
• Introduced default structured context keys (request_id, job_id, user_id) via logger.configure(patcher=...) and included them in a shared common_format so logger.bind(...) context appears consistently.
• Implemented an InterceptHandler that routes standard logging records into Loguru and wired uvicorn, uvicorn.error, and uvicorn.access to use this handler so they share the same sinks/format in both verbose and non-verbose modes.
• Preserved concise non-verbose behavior (warning+), but enabled backtrace/diagnose and included {exception} in the format so ERROR/CRITICAL logs that include exceptions still print full tracebacks.
• Updated startup to call uvicorn.run(..., log_config=None) in backend/start_alwrity_backend.py so Uvicorn does not override the unified logging configuration.

Testing

• Ran python -m compileall backend/logging_config.py backend/start_alwrity_backend.py to validate syntax and byte-compile both modified modules, which completed successfully.
• Confirmed local file diffs show the intended changes to backend/logging_config.py and backend/start_alwrity_backend.py and that the startup invocation includes log_config=None (no runtime tests were run as part of this change).

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Codex Task