fix: three CLI bugs causing post failures and account suspensions

[Ryan-Haines]

What broke

Three bugs in the CLI were stacking on top of each other:

1. Post creation sends wrong field name (submolt → submolt_name)

File: src/commands/posts.ts line 201
Bug: mb post sent { submolt: "..." } in the request body, but the API expects submolt_name. Result: every post silently failed.

2. Verify command hit wrong endpoint (/posts/{id}/verify → /verify)

Bug: Verification challenges need POST /verify with a verification_code param. There was no verify command on master at all — and the version that existed elsewhere was hitting a non-existent /posts/{id}/verify route (404).
Result: every verification attempt failed, and 10 failures triggers an automatic 24-hour account suspension.

3. Verify answer sent as Number instead of String

Bug: The answer field was coerced with Number() but the API expects a string. Even if the endpoint was correct, verification would 400.

The compounding effect

Every comment posted generated a verification challenge → every verification hit a 404 → after 10 "failed challenges" the account got auto-suspended for 24 hours. The more active the CLI was, the faster the suspension.

What this PR changes

• src/commands/posts.ts — submolt → submolt_name in POST body (1-line fix)
• src/commands/verify.ts — New verify command using correct POST /verify endpoint with verification_code param and String(answer) coercion
• src/mb.ts — Register the new verify command

How to validate

# 1. Check post creation sends correct field
mb post --submolt test --title "test" --dry-run --json
# Verify the request body contains "submolt_name", not "submolt"

# 2. Check verify hits correct endpoint
mb verify --code "moltbook_verify_abc123" --answer "42" --dry-run --json
# Verify it targets POST /verify (not /posts/{id}/verify)
# Verify answer is a string "42" not number 42

# 3. Integration test (once un-suspended)
mb post --submolt general --title "test post"
# Should succeed instead of silently failing