Merge branch 'dev', commit 'refs/pull/3621/head' of github.com:router…

…-for-me/CLIProxyAPI into dev

# Conflicts:
#	internal/translator/gemini/openai/responses/gemini_openai-responses_request_test.go

Merge pull request router-for-me#3620 from iBenzene/fix/responses-inp…

…ut-id-dedupe

fix(openai): dedupe response websocket input item IDs

Merge pull request router-for-me#3612 from router-for-me/log

feat(logging): add request_id handling in HomeAppLogForwarder and tests

fix(logging): log errors during file-backed source cleanup

Merge pull request router-for-me#3591 from sususu98/feat/signature-ch…

…eck-extraction

refactor: extract signature validation

feat(usage): add service tier tracking and defaults in usage reporting

- Introduced `service_tier` metadata key to capture client-requested service tiers.
- Updated usage records, context propagation, and plugins to include service tier data.
- Added default handling logic for cases where `service_tier` is absent.
- Implemented tests for `service_tier` extraction, defaults, and updates across components.

feat(usage): include cache tokens in total token calculation and add …

…tests

- Updated `TotalTokens` calculation to account for `CacheReadTokens` and `CacheCreationTokens`.
- Added tests to validate accurate token aggregation and fallback behavior for `CachedTokens`.

feat(logging): improve file-backed source cleanup and directory recre…

…ation logic

- Added `assertFileBodySourceCleaned` helper to streamline cleanup validations in tests.
- Introduced handling to recreate missing directories during file source operations.
- Enhanced tests to verify behavior after manual directory removal, ensuring robustness.
- Fixed edge cases in log file merging when parts are missing.

feat(executor): add TTFT tracking and reporting for enhanced performa…

…nce metrics

- Introduced Time-To-First-Token (TTFT) measurement and reporting across major executors.
- Added TTFT calculation to `UsageReporter`, including support for HTTP clients and WebSocket communication.
- Updated tests to validate TTFT tracking in streamed and non-streamed scenarios.
- Ensured integration with `usage` plugin and augmented usage records with TTFT data.

feat(images): add support for configurable GPT Image 2 base model and…

… improved SSE handling

- Introduced `GPTImage2BaseModel` configuration for hosted image generation tools with validation for "gpt-" prefix.
- Added logic to dynamically resolve and apply the base model in Codex executor workflows.
- Enhanced server-sent events (SSE) implementation with keep-alive tickers and error events for stream reliability.
- Updated configuration file examples and internal documentation.