feat(blog): add markdown blog sourced from a gitea repo

posts are markdown files with yaml frontmatter (title, slug, date;
optional draft/public) in the grenade/blog repo. the worker's new
BlogSource polls the repo — one branch-tip request when nothing
changed — and upserts posts into events with source='blog' and
occurred_at from the frontmatter date, so imported posts keep their
original publish dates and backfill the contribution graph.

- new /v1/blog and /v1/blog/{slug} endpoints over the existing
  EventReader port; drafts stay hidden via the public gate
- new /blog and /blog/:slug routes, nav link, activity-feed entry
  with post icon and filter toggle; relative image srcs resolve to
  gitea raw urls
- shared Markdown component extracted from ProjectPage
- vite proxy target overridable via API_PROXY_TARGET for local dev

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CLAUDE.md

@@ -37,7 +37,7 @@ moments-worker     — ingestion daemon binary (runs migrations, connects as mom
 
 React 19 + Vite 6 (SWC) + TypeScript + Bootstrap 5. State/data via `@tanstack/react-query`. Package manager is **pnpm**.
 
-Routes: `/` (dashboard), `/activity` (timeline), `/project/:source/*` (project detail), `/cv` (resume).
+Routes: `/` (dashboard), `/activity` (timeline), `/project/:source/*` (project detail), `/blog` + `/blog/:slug` (blog), `/cv` (resume).
 
 ## Build & Dev Commands
 
@@ -71,7 +71,9 @@ PostgreSQL with three migrations in `crates/moments-data/migrations/`. Two roles
 
 ## API Endpoints
 
-All under `/v1/`: `healthz`, `events`, `sources`, `projects`, `activity/daily`, `forge/{source}/*`, `og/contributions.png`.
+All under `/v1/`: `healthz`, `events`, `sources`, `projects`, `blog`, `blog/{slug}`, `activity/daily`, `forge/{source}/*`, `og/contributions.png`.
+
+Blog posts are markdown files with YAML frontmatter (`title`, `slug`, `date`; optional `draft`/`public`) in the `grenade/blog` Gitea repo. The worker's `BlogSource` polls the repo (branch-tip sha as change detection) and upserts posts into `events` with `source='blog'` and `occurred_at` from the frontmatter date, so imported posts keep their original publish dates. Publishing or editing a post = pushing to that repo.
 
 ## Deployment