DBP-91: 在後端導入 PostHog

[pan93412]

• feat: send events to PostHog
• test: update test for new EventService signature
• fix(server): inject PostHogClient
• feat(events): send point grant event to PostHog
• test(events): fix tests

[linear]

DBP-91 在後端導入 PostHog

[Copilot]

Pull Request Overview

This PR introduces PostHog analytics integration to the backend system, enabling event tracking and analytics data collection. The changes add PostHog as a dependency and update the event handling system to send events to PostHog alongside existing database operations.

Key changes:

• Added PostHog client configuration and initialization
• Updated EventService and PointsGranter to accept PostHog client
• Implemented event sending to PostHog for user actions and point grants

Reviewed Changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
go.mod	Added posthog-go dependency
internal/config/models.go	Added PostHog configuration structure with validation
docs/config.md	Added PostHog configuration documentation
cmd/backend/dependencies.go	Added PostHog client initialization and lifecycle management
cmd/backend/server.go	Registered PostHog client in dependency injection
internal/events/events.go	Updated EventService to send events to PostHog
internal/events/points.go	Updated PointsGranter to send point grant events to PostHog
Multiple test files	Updated test constructors to pass nil PostHog client

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[Copilot]

Pull Request Overview

Copilot reviewed 16 out of 17 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull Request Overview

Copilot reviewed 17 out of 18 changed files in this pull request and generated 1 comment.

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