Add TypeScript strict mode to both client and backend tsconfig

[Calebux]

Description

Neither /backend/tsconfig.json nor /client/tsconfig.json enables TypeScript strict mode. Without strict mode, common bugs like null/undefined dereferences, implicit any parameters, and uninitialized class properties go undetected at compile time.

Current State

// tsconfig.json (likely)
{
  "compilerOptions": {
    "strict": false  // or not set
  }
}

Fix

Enable strict mode

{
  "compilerOptions": {
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "exactOptionalPropertyTypes": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true
  }
}

The strict flag enables:

• strictNullChecks — catches null/undefined bugs
• strictFunctionTypes — proper function type variance
• strictBindCallApply — type-safe bind/call/apply
• strictPropertyInitialization — catches uninitialized class fields
• noImplicitAny — forces explicit types

Migration Strategy (incremental)

Enabling strict on a large codebase will produce many errors. Use incremental migration:

Step 1: Enable strictNullChecks only

Fix all null/undefined errors first. This has the highest ROI for bug prevention.

Step 2: Enable noImplicitAny

Fix all implicit any types.

Step 3: Enable full strict: true

For each step: use // @ts-expect-error with a TODO comment for errors you can't fix immediately, tracking them as tech debt.

Why This Matters for SYNCRO

The subscription service currently uses any types extensively. With strictNullChecks, the compiler would have caught potential null dereferences on subscription fields before they cause runtime errors.

Acceptance Criteria

• strictNullChecks: true enabled in both tsconfigs
• All null/undefined errors resolved (no !. non-null assertions on untrusted data)
• noImplicitAny: true enabled
• TypeScript compilation still passes in CI after changes
• Remaining strict violations tracked as issues

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[devxsameer]

@devxsameer has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I’d like to work on this issue. I’m a backend-leaning full stack developer, and I’ve already completed 6 issues in Wave 1 and 15 issues in Wave 2. I can help enable strict TypeScript checks in both client and backend tsconfig files, handle the migration incrementally, fix the highest-priority type safety issues, and keep the build passing while tracking any remaining strict-mode debt clearly.

ETA: 3–4 hours.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @devxsameer to this issue.

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Congratulations, @devxsameer! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @devxsameer: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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