* refactor: replace set_gemini_safety_settings() with LLMProvider.with_config()
Removes the fragile ContextVar-setter pattern where callers had to remember
to call set_gemini_safety_settings() at every operation entry point.
Instead, LLMProvider.with_config(resolved_config) returns a
ConfiguredLLMProvider wrapper that:
- injects per-bank settings (Gemini safety settings) on every call via
token-based ContextVar set/reset — properly scoped, no leakage
- proxies all attribute access to the underlying provider via __getattr__
- requires zero changes to LLMInterface or any provider implementations
Call sites (retain, reflect, consolidation) now pass
llm_config.with_config(resolved_config) to sub-components instead of
setting a global context var and hoping nothing else runs in between.
This pattern also composes naturally with a future per-bank provider
factory: callers always receive something with a .call() method.
* fix: pass messages/tools as kwargs in ConfiguredLLMProvider to preserve class-level patch compatibility
Adds per-bank configurable safety settings for Gemini/Vertex AI:
- New `HINDSIGHT_API_LLM_GEMINI_SAFETY_SETTINGS` env var (JSON array)
- Hierarchical config field so banks can override via Config API
- ContextVar pattern for zero-signature-change per-request override
- All 6 thresholds supported: UNSPECIFIED, OFF, BLOCK_NONE, BLOCK_LOW_AND_ABOVE, BLOCK_MEDIUM_AND_ABOVE, BLOCK_ONLY_HIGH
- UI: Models > Gemini/Vertex AI section with per-category threshold selectors and link to Google docs
- Graceful handling when bank_config_api feature is disabled
- 12 new tests covering config parsing, GeminiLLM behaviour, and context var override
