refactor: Extract duplicated code patterns into shared utilities

[devin-ai-integration]

Summary

Eliminates ~380 lines of duplicated code across the backend controllers and frontend by extracting recurring patterns into reusable shared utilities.

Backend — new shared utilities:

Utility	Purpose
asyncHandler(fn)	Wraps async controllers to auto-catch errors → 500 { message: "Error in server" }. Removes ~25 identical try/catch blocks.
prismaSelects.ts	Typed Prisma select constants (repoSummarySelect, issueDetailSelect, userSummarySelect, commentDetailSelect) — previously copy-pasted 4-5x each.
findRepoWithAccess(owner, repo, userId?)	Repo lookup with public/owner visibility check — was duplicated in issue, comment, and fork controllers.
verifyRepoOwner(username, req, res)	Owner lookup + 404/403 guard — was duplicated 3x in repo.controller.ts.
invalidateTokens(access, refresh, res)	Token decode → blacklist → clear cookies — was duplicated in logout, refresh, and delete-user flows.
buildUpdateData(fields, res)	Filters truthy fields into update object, returns 400 if empty — was duplicated in update-repo, update-issue (2x), update-user.
validate middleware	Reusable Zod validation for params/query/body (available for future route-level usage).

Frontend:

• Consolidated UserProfile / Repository interfaces into types/user.ts (was defined separately in useUser.ts and ProfilePage.tsx).
• Removed duplicate getMe API function — auth.api.ts now delegates to getCurrentUserApi from user.api.ts.
• Fixed implicit any type on repo map parameter in ProfilePage.tsx.

Example — before vs after (controller pattern):

// Before: repeated in every handler
export const getMyRepos = async (req, res) => {
  try {
    // ...logic...
    // ...same select object copy-pasted...
  } catch (error) {
    console.log("Error in getMyRepos: ", error);
    res.status(500).json({ message: "Error in server" });
  }
};

// After:
export const getMyRepos = asyncHandler(async (req, res) => {
  // ...logic using repoListItemSelect...
  // error handling is automatic
});

Link to Devin session: https://app.devin.ai/sessions/1f25cda24527464e95ff67b60b2e1f9b
Requested by: @amnkarn

[devin-ai-integration]

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