feat(phase4): implement Tasks 4.1 and 4.2 - Pairing & Cron

Task 4.1: Pairing Protocol & Secret Store
- PairingGuard: HMAC-based token exchange for device pairing
  - Time-limited tokens with configurable expiry
  - Persistent paired device storage (JSON)
  - Token consumption prevents reuse
- SecretStore: Encrypted secret storage using AES-GCM
  - File-based persistence with chmod 600 on Unix
  - Key derivation from master key file
  - Supports CRUD operations for secrets

Task 4.2: Cron Scheduler
- ISchedule interface with three implementations:
  - CronScheduleExpr: Standard 5-field cron expressions via Cronos
  - EverySchedule: Fixed interval repetition
  - AtSchedule: One-shot execution at specific time
- CronScheduler: SQLite-backed persistent storage
  - Thread-safe job management
  - Support for due job detection
  - One-shot job auto-deletion
  - Job enable/disable support

All implementations follow TDD with 68 new tests:
- 31 tests for Security (PairingGuard, SecretStore)
- 37 tests for Cron (Schedules, CronScheduler)

Author: smartprogrammer93

ClawSharp.slnx

@@ -10,6 +10,7 @@
     <Project Path="src/ClawSharp.Providers/ClawSharp.Providers.csproj" />
     <Project Path="src/ClawSharp.Tools/ClawSharp.Tools.csproj" />
     <Project Path="src/ClawSharp.UI/ClawSharp.UI.csproj" />
+    <Project Path="src/ClawSharp.Web/ClawSharp.Web.csproj" />
   </Folder>
   <Folder Name="/tests/">
     <Project Path="tests/ClawSharp.Agent.Tests/ClawSharp.Agent.Tests.csproj" />

src/ClawSharp.Gateway/ClawSharp.Gateway.csproj

@@ -15,7 +15,7 @@
     <ProjectReference Include="..\ClawSharp.Channels\ClawSharp.Channels.csproj" />
     <ProjectReference Include="..\ClawSharp.Core\ClawSharp.Core.csproj" />
     <ProjectReference Include="..\ClawSharp.Infrastructure\ClawSharp.Infrastructure.csproj" />
-    <ProjectReference Include="..\ClawSharp.UI\ClawSharp.UI.csproj" />
+    <ProjectReference Include="..\ClawSharp.Web\ClawSharp.Web.csproj" />
   </ItemGroup>
 
 </Project>

src/ClawSharp.Infrastructure/ClawSharp.Infrastructure.csproj

@@ -19,6 +19,8 @@
     <PackageReference Include="Serilog.Sinks.Console" Version="6.1.1" />
     <PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
     <PackageReference Include="Tomlyn" Version="0.20.0" />
+    <PackageReference Include="Cronos" Version="0.9.0" />
+    <PackageReference Include="Microsoft.Data.Sqlite" Version="10.0.3" />
   </ItemGroup>
 
   <PropertyGroup>

src/ClawSharp.Infrastructure/Cron/AtSchedule.cs

@@ -0,0 +1,55 @@
+namespace ClawSharp.Infrastructure.Cron;
+
+/// <summary>
+/// One-shot schedule that fires at a specific time.
+/// Should be deleted after execution.
+/// </summary>
+public sealed class AtSchedule : ISchedule
+{
+    private readonly DateTimeOffset _targetTime;
+
+    public ScheduleKind Kind => ScheduleKind.At;
+
+    /// <summary>Indicates this is a one-shot schedule.</summary>
+    public bool IsOneShot => true;
+
+    /// <summary>The target execution time.</summary>
+    public DateTimeOffset TargetTime => _targetTime;
+
+    /// <summary>
+    /// Creates a one-shot schedule for the specified time.
+    /// </summary>
+    /// <param name="targetTime">The time at which to fire.</param>
+    public AtSchedule(DateTimeOffset targetTime)
+    {
+        _targetTime = targetTime;
+    }
+
+    /// <summary>
+    /// Creates a one-shot schedule from a Unix timestamp in milliseconds.
+    /// </summary>
+    public static AtSchedule FromUnixMilliseconds(long unixMs)
+    {
+        return new AtSchedule(DateTimeOffset.FromUnixTimeMilliseconds(unixMs));
+    }
+
+    public bool IsDue(DateTimeOffset now, DateTimeOffset? lastRun)
+    {
+        // If already fired, never due again
+        if (lastRun.HasValue)
+            return false;
+
+        // Due if target time has passed
+        return now >= _targetTime;
+    }
+
+    public DateTimeOffset? GetNextOccurrence(DateTimeOffset from)
+    {
+        // If target is in the future, return it
+        if (_targetTime > from)
+            return _targetTime;
+
+        // Target has passed, no more occurrences
+        return null;
+    }
+}

src/ClawSharp.Infrastructure/Cron/CronJob.cs

@@ -0,0 +1,31 @@
+namespace ClawSharp.Infrastructure.Cron;
+
+/// <summary>
+/// Represents a scheduled job with a name, schedule, and payload.
+/// </summary>
+public sealed class CronJob
+{
+    /// <summary>Unique name of the job.</summary>
+    public required string Name { get; set; }
+
+    /// <summary>The schedule that determines when the job fires.</summary>
+    public required ISchedule Schedule { get; set; }
+
+    /// <summary>Optional payload data for the job (e.g., JSON, message text).</summary>
+    public string? Payload { get; set; }
+
+    /// <summary>Optional session target for agent execution.</summary>
+    public string? SessionTarget { get; set; }
+
+    /// <summary>When the job was last executed.</summary>
+    public DateTimeOffset? LastRun { get; set; }
+
+    /// <summary>When the job was created.</summary>
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+
+    /// <summary>Whether the job is currently enabled.</summary>
+    public bool Enabled { get; set; } = true;
+
+    /// <summary>Optional metadata for the job.</summary>
+    public Dictionary<string, string>? Metadata { get; set; }
+}

src/ClawSharp.Infrastructure/Cron/CronScheduleExpr.cs

@@ -0,0 +1,60 @@
+using Cronos;
+
+namespace ClawSharp.Infrastructure.Cron;
+
+/// <summary>
+/// Schedule based on a standard cron expression (5 fields).
+/// Supports minute, hour, day of month, month, and day of week.
+/// </summary>
+public sealed class CronScheduleExpr : ISchedule
+{
+    private readonly CronExpression _expression;
+    private readonly string _expressionString;
+    private readonly TimeZoneInfo _timeZone;
+
+    public ScheduleKind Kind => ScheduleKind.Cron;
+
+    /// <summary>The raw cron expression string.</summary>
+    public string Expression => _expressionString;
+
+    /// <summary>
+    /// Creates a cron schedule from the given expression.
+    /// </summary>
+    /// <param name="expression">Cron expression (5 fields: minute hour day-of-month month day-of-week).</param>
+    /// <param name="timeZone">Optional timezone for evaluation. Defaults to UTC.</param>
+    /// <exception cref="ArgumentException">Thrown if the expression is invalid.</exception>
+    public CronScheduleExpr(string expression, TimeZoneInfo? timeZone = null)
+    {
+        ArgumentNullException.ThrowIfNull(expression);
+
+        try
+        {
+            _expression = CronExpression.Parse(expression);
+        }
+        catch (CronFormatException ex)
+        {
+            throw new ArgumentException($"Invalid cron expression: {expression}", nameof(expression), ex);
+        }
+
+        _expressionString = expression;
+        _timeZone = timeZone ?? TimeZoneInfo.Utc;
+    }
+
+    public bool IsDue(DateTimeOffset now, DateTimeOffset? lastRun)
+    {
+        if (lastRun is null)
+            return true;
+
+        // Get the next occurrence after the last run
+        var nextOccurrence = GetNextOccurrence(lastRun.Value);
+
+        // It's due if the next occurrence is at or before now
+        return nextOccurrence.HasValue && nextOccurrence.Value <= now;
+    }
+
+    public DateTimeOffset? GetNextOccurrence(DateTimeOffset from)
+    {
+        var next = _expression.GetNextOccurrence(from.UtcDateTime, _timeZone);
+        return next.HasValue ? new DateTimeOffset(next.Value, TimeSpan.Zero) : null;
+    }
+}