feat(web): build the Today action loop

[seonghobae]

Summary

Implements the first reviewable slice of #62, the current highest-impact buyer gap in #21.

• replaces the static home placeholder with an accessible responsive Today workspace
• captures bounded visible actions using browser-generated UUIDv4 identifiers
• makes the three-priority capacity explicit and enforces it in the domain model
• schedules committed actions in 15-minute increments with bounded durations and deterministic overlap rejection
• records completion evidence without hiding unfinished or completed work
• persists only a versioned browser-local draft, rejects malformed/oversized state, and resets cleanly on the next local day
• labels the local-only trust boundary so users are not misled into believing draft actions are synchronized
• adds pure domain tests for priority limits, opaque identifiers, schedule conflicts, completion, persistence, rollover, duplicate evidence, and ownership-field injection
• adds Playwright evidence for capture-to-completion, reload persistence, priority capacity, keyboard-addressable controls, and mobile viewport usability

Deferred

Authenticated workspace derivation, planning-service synchronization, optimistic concurrency, calendar synchronization, habits/review evidence, offline mutation queues, localization, and production telemetry remain separate slices.

Validation gate

Merge only when CI, AppGuardrail, SAST Semgrep, Security Scan, Commercial Readiness, CodeRabbit, and all human/security review feedback pass on the exact head with no unresolved actionable findings.

Refs #62 and #21.

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📥 Commits

Reviewing files that changed from the base of the PR and between 14886ff and 7d15d7c.

📒 Files selected for processing (9)

• apps/web/app/page.tsx
• apps/web/app/styles.css
• apps/web/app/today-client.tsx
• apps/web/app/today-state.test.ts
• apps/web/app/today-state.ts
• apps/web/app/today-storage.ts
• apps/web/e2e/today-flow.spec.ts
• apps/web/package.json
• apps/web/playwright.config.ts

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