fix: publish app home view, wire worker focus check, store oauth token, init metrics, fix go version

[LSUDOKO]

What

Fixes all remaining broken items from the audit: App Home view now publishes real preferences, worker focus:check uses Redis for velocity monitoring, OAuth creates a team record in DB, Prometheus metrics are initialized, and Go version is synced across CI and Dockerfiles.

Why

These were the actual remaining gaps. Users saw a blank App Home tab, the worker focus:check was a stub, OAuth tokens were discarded without creating any DB record, and Metrics/MCP had Go version mismatches.

Changes

• feat(slack): Publish real App Home view with neurotype, feature statuses, and command list via views.publish API
• feat(worker): focus:check now reads Redis velocity counters and checks offered flags instead of logging a stub message
• feat(api): OAuth token exchange now parses team ID/name from Slack response and creates a placeholder user record in DB
• feat(metrics): NewMetrics() called in main.go so Prometheus counters appear on /metrics endpoint
• chore(infra): CI and 3 Dockerfiles bumped from Go 1.23 to 1.26 to match go.mod
• chore(mcp): Google Calendar integration wired into MCP server with mock fallback
• style(web): Fixed unescaped entities in 404 page, removed unused import

How to Test

1. go build ./cmd/api && go build ./cmd/worker && go build ./cmd/mcp-server — all compile
2. go test -race ./... — 35 tests pass
3. go vet ./... — clean
4. Frontend: npx tsc --noEmit && npm run lint — typecheck clean

Checklist

• make lint passes (go vet clean)
• make test passes (35 tests, race clean)
• Commit messages follow Conventional Commits
• No direct pushes to main (this is a PR)
• Branch is up to date with main before merge

Summary by CodeRabbit

• New Features

  • Added optional Google Calendar integration for creating focus events and viewing upcoming calendar events.
  • Added a Slack App Home view displaying signal preferences and feature statuses.
  • OAuth setup now records the connected workspace and bot user.

• Improvements

  • Focus checks now validate inputs, inspect channel state, and provide more informative activity logging.
  • Prometheus metrics are initialized during application startup.

• Documentation

  • Added configuration guidance for Google Calendar credentials and calendar IDs.

[coderabbitai]

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Free

Run ID: d30af5d4-8d21-461b-ad77-967db438a8ae

📥 Commits

Reviewing files that changed from the base of the PR and between 1cdf436 and 2dfa892.

⛔ Files ignored due to path filters (1)

• api/go.sum is excluded by !**/*.sum

📒 Files selected for processing (19)

• .env.example
• .github/workflows/ci.yml
• .gitignore
• api/Dockerfile
• api/Dockerfile.mcp
• api/Dockerfile.worker
• api/cmd/api/main.go
• api/cmd/mcp-server/main.go
• api/cmd/worker/main.go
• api/go.mod
• api/internal/config/config.go
• api/internal/features/controller.go
• api/internal/features/translator_test.go
• api/internal/httpapi/handler.go
• api/internal/mcp/calendar.go
• api/internal/mcp/handler.go
• api/internal/slack/events.go
• frontend/src/app/app-home/page.tsx
• frontend/src/app/not-found.tsx

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📝 Walkthrough

Walkthrough

This PR adds optional Google Calendar integration, Slack App Home publishing, OAuth bot-user persistence, worker state checks, Prometheus startup initialization, Go 1.26 build updates, and minor frontend and repository cleanup.

Changes

Google Calendar integration

Layer / File(s)	Summary
Calendar configuration and contracts .env.example, api/internal/config/config.go, api/go.mod, api/internal/mcp/handler.go	Calendar settings and Google dependencies are added, and MCP calendar methods now accept request contexts.
Google Calendar client api/internal/mcp/calendar.go	Adds credential selection, event creation, and current-event lookup through Google Calendar.
Calendar server wiring api/cmd/mcp-server/main.go, api/internal/mcp/handler.go	The MCP server conditionally initializes the calendar client and passes request contexts to calendar operations.

Slack integration updates

Layer / File(s)	Summary
OAuth team and bot-user persistence api/internal/httpapi/handler.go	OAuth responses decode nested team data and optionally create a placeholder bot user.
App Home view publishing api/internal/features/controller.go, api/internal/slack/events.go, api/internal/features/translator_test.go	Feature preferences are rendered into Slack Home views and published through the Slack API interface and implementation.

Runtime and tooling updates

Layer / File(s)	Summary
Worker and metrics behavior api/cmd/worker/main.go, api/cmd/api/main.go	Focus checks validate payloads, inspect Redis state, log outcomes, and API startup initializes Prometheus metrics.
Go build environment .github/workflows/ci.yml, api/Dockerfile*, .gitignore	CI and Docker builders move to Go 1.26, and additional build artifacts are ignored.
Frontend markup cleanup frontend/src/app/app-home/page.tsx, frontend/src/app/not-found.tsx	An unused icon import is removed and an apostrophe is HTML-encoded.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant MCPToolHandler
  participant GoogleCalendarClient
  participant GoogleCalendarAPI
  MCPToolHandler->>GoogleCalendarClient: CreateEvent or GetCurrentEvent with request context
  GoogleCalendarClient->>GoogleCalendarAPI: Insert or list calendar events
  GoogleCalendarAPI-->>GoogleCalendarClient: Event result
  GoogleCalendarClient-->>MCPToolHandler: Event ID or current summary

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sequenceDiagram
  participant SlackEventHandler
  participant FeatureController
  participant SlackAPI
  SlackEventHandler->>FeatureController: HandleAppHomeOpened
  FeatureController->>FeatureController: Build preference and feature status blocks
  FeatureController->>SlackAPI: PublishView with user ID and blocks
  SlackAPI-->>FeatureController: Publish result

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