Fix: Prevent 500 POST errors via strict frontend schema validation during Round Creation

[ayushshukla1807]

Fixes #447.
Resolves Server 500 errors occurring when organizers attempted to submit NewCampaign or NewRound forms missing heavily required parameters that the DAO refused.

Technical Solution

I implemented a strict client-side validation schema inside the Campaign and Round form components. By asserting required parameter rules natively in the Vue bindings before the final Axios dispatch, we successfully prevent malformed UI packets from triggering catastrophic backend stack traces.

The guards are enforced in the following order:

1. Deadline presence — blocks submission if deadline_date is null
2. Round name — blocks empty or whitespace-only names
3. Quorum/juror consistency — blocks invalid quorum values or quorum > 0 with 0 jurors assigned
4. Import source — blocks category/CSV/file-list fields being empty on Round 1
5. Threshold — blocks subsequent rounds advancing without a threshold selected

Architectural Diagram

sequenceDiagram
    participant User
    participant Form as Vue Template (RoundNew.vue)
    participant Guard as submitRound() Guard
    participant Axios as adminService

    User->>Form: Clicks Add Round (empty fields)
    Form->>Guard: Invokes submitRound()
    Guard-->>Form: Deadline missing? alertService.error()
    Guard-->>Form: Name empty? alertService.error()
    Guard-->>Form: Quorum invalid? alertService.error()
    Guard-->>Form: Category missing? alertService.error()
    Note over Guard: All guards pass
    Guard->>Axios: adminService.addRound(payload)
    Axios-->>Form: 200 OK

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Verification (Local Dev)

Tested locally on http://localhost:5173 against a live Flask backend on port 5005.

Scenario	Expected	Result
Submit with no deadline	Error toast shown, no Axios call	✅ Pass
Submit with blank name	Error toast shown, no Axios call	✅ Pass
Submit with empty category	Error toast shown, no Axios call	✅ Pass
Submit with valid fields	Round created successfully	✅ Pass