feat: add topic pub/sub dashboard view

[pratyush618]

Summary

• Adds a Topics view to the dashboard for pub/sub observability
• Topics list: subscription count, total backlog, dead-letter depth per topic
• Topic detail: per-subscription task, queue, active/paused and durable/ephemeral badges, pending/running/dead counts, and oldest-pending age
• Pause, resume, and unsubscribe actions on each subscription

Changes

• Server: handlers/topics.py (GET /api/topics aggregation, GET /api/topics/:topic detail, pause/resume/unsubscribe routes; adds the DELETE 2-capture route table), backed by queue.topic_stats()
• SPA: features/topics/ feature folder (api, hooks with the shared refresh interval, tables) plus list and detail routes and a Topics nav entry
• Read-only path plus actions; polling via the existing refresh-interval convention

Test plan

• Server: aggregation math, detail filtering, unknown-topic empty, pause/resume, unsubscribe
• SPA: typecheck, lint, tests, build all green

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: bdb7c7c5-070b-4dc6-a190-9f8adede8b02

📥 Commits

Reviewing files that changed from the base of the PR and between 446d140 and 51086ef.

📒 Files selected for processing (16)

• dashboard/src/components/layout/nav-config.ts
• dashboard/src/features/topics/api.ts
• dashboard/src/features/topics/components/index.ts
• dashboard/src/features/topics/components/subscriptions-table.tsx
• dashboard/src/features/topics/components/topics-table.tsx
• dashboard/src/features/topics/derived.test.ts
• dashboard/src/features/topics/derived.ts
• dashboard/src/features/topics/hooks.ts
• dashboard/src/features/topics/index.ts
• dashboard/src/lib/api-types.ts
• dashboard/src/routes/topics.tsx
• dashboard/src/routes/topics_.$topic.tsx
• sdks/python/taskito/dashboard/handlers/topics.py
• sdks/python/taskito/dashboard/routes.py
• sdks/python/taskito/dashboard/server.py
• sdks/python/tests/dashboard/test_topics_api.py

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/pubsub-dashboard

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