refactor(terminology): replace user-facing "blog" → "post" across docs and packages

[haroonwaves]

Motivation

• Standardize user-facing terminology from "blog" to "post" across docs and component APIs to better reflect wording while keeping project/package names intact.
• Ensure code and documentation examples remain consistent so consumers use Post* types and components when integrating the library.

Description

• Replaced user-facing strings and docs (app/content/*, README.md, etc.) from "blog" to "post" and updated examples to use post paths and config keys like postSubdirectory.
• Renamed core types and APIs: BlogMeta → PostMeta, Blog → Post, BlogConfig → PostConfig, extractBlogMeta → extractPostMeta, extractBlog → extractPost, getAllBlogsMeta → getAllPostsMeta, and getBlog → getPost in packages/blog-kit-core.
• Renamed React package components and hook files/exports to Post* (BlogRenderer→PostRenderer, BlogCard→PostCard, BlogList→PostList, BlogPlaceholder→PostPlaceholder, useBlogs→usePosts) and updated packages/blog-kit-react/src/index.ts exports accordingly.
• Adjusted app usage to remain compatible (added local aliases where needed and updated blogSubdirectory → blogSubdirectory/postSubdirectory usage in calls) and fixed related type errors so the monorepo type-checks cleanly; branding (blog-kit, package names) was intentionally preserved.

Testing

• Ran pnpm type-check (workspace) and it completed successfully with no TypeScript errors.
• Ran pnpm format:check and Prettier reported all matched files use the configured code style.
• Both automated checks passed after the refactor.

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Codex Task

[cloudflare-workers-and-pages]

Deploying blog-kit with    Cloudflare Pages

Latest commit:	2e8f8c2
Status:	✅  Deploy successful!
Preview URL:	https://f208a947.blog-kit.pages.dev
Branch Preview URL:	https://codex-replace-all-blog-refer.blog-kit.pages.dev

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[chatgpt-codex-connector]

Import renamed Post APIs directly in docs pages

This file still imports getAllBlogsMeta, getBlog, and BlogRenderer (aliased to Post names), but the same commit removes those Blog-prefixed exports from packages/blog-kit-core/src/parser.ts and packages/blog-kit-react/src/index.ts; as soon as the app resolves to the updated package version (the dependency ranges are caret-based), these imports become missing exports and the docs build fails. Switching these imports to getAllPostsMeta, getPost, and PostRenderer avoids that version-skew breakage.

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