feat: Implement air-gap functionality with timeline impact and evidence snapshot services

- Added AirgapTimelineImpact, AirgapTimelineImpactInput, and AirgapTimelineImpactResult records for managing air-gap bundle import impacts.
- Introduced EvidenceSnapshotRecord, EvidenceSnapshotLinkInput, and EvidenceSnapshotLinkResult records for linking findings to evidence snapshots.
- Created IEvidenceSnapshotRepository interface for managing evidence snapshot records.
- Developed StalenessValidationService to validate staleness and enforce freshness thresholds.
- Implemented AirgapTimelineService for emitting timeline events related to bundle imports.
- Added EvidenceSnapshotService for linking findings to evidence snapshots and verifying their validity.
- Introduced AirGapOptions for configuring air-gap staleness enforcement and thresholds.
- Added minimal jsPDF stub for offline/testing builds in the web application.
- Created TypeScript definitions for jsPDF to enhance type safety in the web application.

src/Concelier/StellaOps.Concelier.WebService/Options/ConcelierOptions.cs

@@ -27,6 +27,12 @@ public sealed class ConcelierOptions
 
     public StellaOpsCryptoOptions Crypto { get; } = new();
 
+    /// <summary>
+    /// Air-gap mode configuration.
+    /// Per CONCELIER-WEB-AIRGAP-56-001.
+    /// </summary>
+    public AirGapOptions AirGap { get; set; } = new();
+
     public sealed class StorageOptions
     {
         public string Driver { get; set; } = "mongo";