feat: improve generation analytics and maintenance

backend/app/schemas/story_schemas.py

@@ -220,21 +220,33 @@ class GenerationProviderStatResponse(BaseModel):
     estimated_cost_usd: float = 0.0
 
 
+class GenerationProviderFailureReasonResponse(BaseModel):
+    """Aggregated failed provider call reason."""
+
+    reason: str
+    count: int
+
+
 class GenerationProviderStatsResponse(BaseModel):
     """Provider call stats aggregated from generation job events."""
 
     story_id: int
+    window_days: int | None = None
+    capability: str | None = None
     total_calls: int
     successful_calls: int
     failed_calls: int
     avg_latency_ms: float | None = None
     estimated_cost_usd: float = 0.0
     by_provider: list[GenerationProviderStatResponse] = Field(default_factory=list)
+    failure_reasons: list[GenerationProviderFailureReasonResponse] = Field(default_factory=list)
 
 
 class GenerationProviderAnalyticsResponse(BaseModel):
     """Provider call stats aggregated across one user's generation history."""
 
+    window_days: int | None = None
+    capability: str | None = None
     total_calls: int
     successful_calls: int
     failed_calls: int
@@ -243,6 +255,33 @@ class GenerationProviderAnalyticsResponse(BaseModel):
     job_count: int
     story_count: int
     by_provider: list[GenerationProviderStatResponse] = Field(default_factory=list)
+    failure_reasons: list[GenerationProviderFailureReasonResponse] = Field(default_factory=list)
+
+
+class GenerationRecentFailureResponse(BaseModel):
+    """One recent failed generation task for operations summary."""
+
+    job_id: str
+    story_id: int | None = None
+    story_title: str | None = None
+    output_mode: str
+    current_step: str
+    error_message: str | None = None
+    failure_label: str
+    updated_at: datetime
+
+
+class GenerationOpsSummaryResponse(BaseModel):
+    """Recent generation health summary for one user."""
+
+    window_hours: int
+    stale_threshold_minutes: int
+    active_jobs: int
+    stale_running_jobs: int
+    failed_jobs: int
+    degraded_jobs: int
+    asset_retry_jobs: int
+    recent_failures: list[GenerationRecentFailureResponse] = Field(default_factory=list)
 
 
 class AchievementItem(BaseModel):