FE: Submit work flow (on-chain anchor) + withdraw submission

[0xdevcollins]

Context

Part of the Bounty Builder Lifecycle milestone (v1 boundless). After entry (claim/join/selection), the builder submits their work, which is anchored on-chain.

Blueprint to mirror

• components/hackathons/submissions/SubmissionForm.tsx + SubmissionAnchorProgress.tsx
• features/hackathons/api/use-submission-anchor.ts (participant anchor via the runner)

Tasks

• Submission form: contentUri (PR / repo / writeup / demo link per the bounty's deliverable) -> submit escrow op (useEscrowOpRunner, participant, default MANAGED) + an anchor progress dialog (draft -> on-chain -> confirmed) with tx hash.
• Withdraw submission (withdraw-submission escrow op) before the deadline.
• Guard by bounty status + submission deadline + entry eligibility (claimed/joined/selected/shortlisted).

Acceptance criteria

• Submit anchors on-chain and reaches confirmed; withdraw works; flows are correctly guarded.

Depends on

• Bounty data layer; apply/join/claim flow.

[linear]

BOU-274

[coderabbitai]

🔗 Related PRs

#451 - UI fixes [merged]
#547 - fix(submissions): improve link validation UX, banner display, and error toasts [merged]
#555 - feat(hackathons): add "hidden until results" submission visibility mode [merged]
#582 - fix(rewards): match track winners by submissionId, not participantId [merged]
#586 - fix(submissions): unbreak submission detail page + publish hackathon recap [merged]

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[Ojas2095]

/claim

I'd like to take this on! Reviewing the repository right now and will submit a PR shortly.

[Benjtalkshow]

Done in #649 (merged into feat/t-replace). Closing manually since auto-close only fires on merges to the default branch.