debug: upgrade logging levels for fallback diagnostics

Change fallback LLM creation and invocation logs from DEBUG to WARNING level
so they appear in Robot Framework test output. Also enhance error message to
clearly show which provider failed and why.

This change makes it possible to diagnose why the fallback is not working
by seeing the actual logs in test output instead of having them filtered
as DEBUG level messages.

Logs now include:
- 'Creating fallback LLM instance: anthropic/claude-sonnet-4-20250514'
- 'Fallback LLM created, attempting invocation'
- 'Using cached fallback LLM, attempting invocation'
- 'FALLBACK PROVIDER FAILED: anthropic/claude-sonnet-4-20250514 returned error: [error details]'

This will help diagnose why E2E tests fail with 'both providers exhausted'
when Anthropic should have available credits.

src/cleveragents/application/services/strategy_actor.py

@@ -587,29 +587,29 @@ class StrategyActor:
                 try:
                     # Create or reuse cached fallback LLM
                     if self._fallback_llm is None:
-                        self._logger.debug(
-                            "Creating fallback LLM instance",
+                        self._logger.warning(
+                            "Creating fallback LLM instance: %s/%s",
+                            _FALLBACK_PROVIDER,
+                            _FALLBACK_MODEL,
                             plan_id=plan_id,
-                            fallback_provider=_FALLBACK_PROVIDER,
-                            fallback_model=_FALLBACK_MODEL,
                         )
                         self._fallback_llm = self._registry.create_llm(
                             provider_type=_FALLBACK_PROVIDER,
                             model_id=_FALLBACK_MODEL,
                         )
-                        self._logger.debug(
-                            "Fallback LLM instance created successfully",
+                        self._logger.warning(
+                            "Fallback LLM created, attempting invocation",
                             plan_id=plan_id,
                         )
                     else:
-                        self._logger.debug(
-                            "Reusing cached fallback LLM instance",
+                        self._logger.warning(
+                            "Using cached fallback LLM, attempting invocation",
                             plan_id=plan_id,
                         )
                     content = self._invoke_llm_with_retry(
                         self._fallback_llm, messages, plan_id
                     )
-                    self._logger.info(
+                    self._logger.warning(
                         "Quota error recovery successful with fallback provider",
                         plan_id=plan_id,
                         fallback_provider=_FALLBACK_PROVIDER,
@@ -618,12 +618,12 @@ class StrategyActor:
                 except Exception as fallback_exc:
                     # Log the actual fallback error with full context
                     self._logger.error(
-                        "Fallback provider invocation failed",
+                        "FALLBACK PROVIDER FAILED: %s/%s returned error: %s [%s]",
+                        _FALLBACK_PROVIDER,
+                        _FALLBACK_MODEL,
+                        str(fallback_exc),
+                        type(fallback_exc).__name__,
                         plan_id=plan_id,
-                        fallback_provider=_FALLBACK_PROVIDER,
-                        fallback_model=_FALLBACK_MODEL,
-                        fallback_error=str(fallback_exc),
-                        fallback_error_type=type(fallback_exc).__name__,
                         exc_info=True,
                     )
                     # Re-raise the original exception to let the caller handle it