Consolidate duplicated types into @repo/shared package

[Kuses129]

Summary

Response types and query param interfaces are duplicated between the frontend (apps/web/src/api/) and backend (apps/api/src/modules/), despite a shared package (@repo/shared) already existing and being wired up as a dependency of both apps.

Duplicated Types

Type	Frontend	Backend	Overlap
Organization	Organization	OrganizationResponse	Identical
Repository	Repository	RepositoryResponse	Identical
PullRequest	PullRequest	PullRequestResponse	~90% (cycleTime shape differs slightly)
MergeFrequency	MergeFrequencyResponse	MergeFrequencyResponse	Identical
Query Params	Plain interfaces (e.g. PullRequestsQueryParams)	class-validator DTO classes (e.g. PullRequestListQueryDto)	Same shape, different runtime needs

Proposed Approach

1. Response types — Move shared response interfaces (Organization, Repository, PullRequest, MergeFrequencyResponse, etc.) into @repo/shared and have both apps import from there.
2. Query param interfaces — Define base interfaces in @repo/shared. The backend DTO classes should implements the shared interface while keeping their class-validator decorators for runtime validation. The frontend imports the plain interface directly.
3. PullRequest alignment — Unify the CycleTime shape so both sides use the same definition. The backend's richer CycleTimeResponse (with breakdown fields) can extend a base CycleTime type in shared.

Current State of @repo/shared

The package infrastructure is ready (package.json, TypeScript build, exports configured, included in both app dependencies). It currently only exports:

• HealthResponse
• PaginatedResponse<T>
• CursorPaginationParams

Acceptance Criteria

• All identical response types live in @repo/shared (single source of truth)
• Both apps/api and apps/web import these types from @repo/shared
• No duplicated type definitions remain across apps
• Backend DTOs implement shared interfaces for query params
• Existing functionality unchanged (no runtime impact)