docs: refresh feature management + full quickstart for single-panel flow (Batch 5, SCHX-535) (#353)

* docs: update feature setup copy for single-panel create flow (SCHX-535)

The Create/Edit feature UI is now a single scrolling side panel (name,
description, type, flag key, and event in one form with a single "Create
feature" button), replacing the old multi-step "Continue" modal. Rewrite
the "Setting up Features" steps in features.mdx to match and consolidate
the create-flow images from three to two. Tweak the tracking-usage Event
step to reference the Event section in the edit panel.

Screenshot refreshes for this batch (feature homepage, policy, flag tab,
usage tab, create flow, entitlement editor) follow in a separate commit.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Refresh feature-management screenshots for current UI

Recapture the 9 feature-management and quickstart feature screenshots
from the live app to match the current single-panel feature create/edit
flow and version-aware UI. Pairs with the copy rewrite in 69d7be0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* remove unused items

* Update quickstart guide copy for current UI; remove orphaned images

Rewrite the quickstart feature flows to match the single-panel feature
create/edit UI (was a multi-step "Continue" modal) and the current
left-hand navigation and Monetization Settings entitlement editor:

- entitling-a-feature: single-panel boolean create + click-a-plan entitle
- tracking-usage: single-panel event create (flag + event) + numerical
  usage entitlement via the Monetization Settings panel
- account-setup: Settings is the gear at the bottom of the left nav,
  not a top-right gear icon
- create-a-component: match the "Define component" dialog (name, then
  Choose template) and "Create Component" button label
- setup-sdk: fix "Add Pns" typo and drop the stray bare list item

Delete 5 orphaned quickstart screenshots no longer referenced by any
page (components-builder, plan-audience, plan-creation, plan-mapping,
stripe-import).

Screenshot refreshes for the referenced quickstart images follow in a
separate commit.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Refresh quickstart screenshots to match current app and account

Recapture all 13 referenced quickstart images from the live
DashAI/Production account: boolean feature create + entitlement
(single-panel flow, Monetization Settings), event feature create +
entitlement, API keys list, both component-builder steps, the pricing
table preview, and the company last-seen header.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Align entitlement copy with the refreshed screenshots

The entitlement screenshots illustrate the Entitlements tab and
Monetization Settings panel using existing features (Video Generation,
AI Conversations) on real plans, so reword the steps to describe what
the images actually show and drop the stale "Demo Plan" reference. Also
make the usage allowance generic instead of hardcoding 25, which no
longer matched the example.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ryanechternacht