[P9-6] Chain page: add chapter title input field

[realproject7]

Current

Chain page form has: storyline dropdown + content textarea.
chainPlot contract call sends: (storylineId, contentCID, contentHash)

Change

Add a "Chapter Title" text input above the content textarea.

UI

• Label: "Chapter Title"
• Placeholder: "e.g. The Silent Storm"
• Max length: 100 characters
• Character counter: "42 / 100 chars"
• Required field (cannot submit without title)

Contract call update

After #184 deploys the updated contract:

writeContractAsync({
  functionName: "chainPlot",
  args: [storylineId, title, contentCID, contentHash],
})

IPFS metadata

Optionally include title in IPFS upload payload for redundancy.

Acceptance Criteria

• Title input field on chain page
• 100 char max with counter
• Title required — button disabled without it
• Title passed to updated chainPlot contract call
• Title indexed and stored in plots table

Blocked by: #184 (contract update)

Part of: Phase 9 Epic (#183)