[Sprint] Issues: Refactor handlers to use ObjectId and return Result<T>

[mpaulosky]

Problem

Issue handlers (Get, List, Create, Update, Delete, UpdateStatus) do not return Result to the API layer. They throw exceptions instead of returning typed results. They also do runtime ObjectId.TryParse() which should move to the validation layer (handled by Issue #1).

Depends On

Depends on: Foundation issue (standardize ObjectId in Shared commands/queries)

Files to Modify

• src/Api/Handlers/Issues/GetIssueHandler.cs — return Task<Result>
• src/Api/Handlers/Issues/ListIssuesHandler.cs — return Task<Result<IReadOnlyList>>
• src/Api/Handlers/Issues/CreateIssueHandler.cs — return Task<Result>
• src/Api/Handlers/Issues/UpdateIssueHandler.cs — return Task<Result>
• src/Api/Handlers/Issues/DeleteIssueHandler.cs — return Task<Result>
• src/Api/Handlers/Issues/UpdateIssueStatusHandler.cs — return Task<Result>
• src/Api/Handlers/Issues/IssueEndpoints.cs — map Result → HTTP responses (200/201/404/409/500)

Acceptance Criteria

• All 6 Issue handlers return Task<Result>
• No ObjectId.TryParse() calls in handler bodies (parsing done by validator)
• IssueEndpoints.cs maps Result success → 200/201, Result failure → appropriate HTTP status
• 404 returned when issue not found (was: null returned or exception thrown)
• Solution builds with zero errors and zero warnings

[github-actions]

🏗️ Squad Triage — Aragorn (Lead)

Issue: #81 — [Sprint] Issues: Refactor handlers to use ObjectId and return Result
Assigned to: Legolas (Frontend Dev)
Reason: Issue relates to frontend/UI work

@copilot evaluation: No strong capability match — routed to squad member.

Team roster:

• Aragorn (Lead) → label: squad:aragorn
• Legolas (Frontend Dev) → label: squad:legolas
• Sam (Backend Dev) → label: squad:sam
• Gimli (Tester) → label: squad:gimli
• Boromir (DevOps) → label: squad:boromir
• Frodo (Tech Writer) → label: squad:frodo
• Gandalf (Security Officer) → label: squad:gandalf
• Ralph (Work Monitor) → label: squad:ralph
• @copilot (🤖 Coding Agent) → label: squad:@copilot
• @copilot (Coding Agent) → label: squad:copilot

To reassign, remove the current squad:* label and add the correct one.

[github-actions]

📋 Assigned to Sam (Backend Dev)

Issue: #81 — [Sprint] Issues: Refactor handlers to use ObjectId and return Result

Sam will pick this up in the next Copilot session.

For Copilot coding agent: If enabled, this issue will be worked automatically.
Otherwise, start a Copilot session and say:
Sam, work on issue #81