feat: LinkedIn video upload support (linkedin_upload_video tool + REST route)

Implements full 4-step LinkedIn Videos API flow: download from public URL,
initialize upload, 4MB chunk PUT with ETag collection, finalize, poll until
AVAILABLE, then publish via POST /rest/posts reading post ID from x-restli-id.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.planning/phases/01-linkedin-video-upload/01-01-SUMMARY.md

@@ -0,0 +1,22 @@
+# Phase 01 Plan 01: LinkedIn Video Upload Client Summary
+
+**Added `linkedinRestRequest`, `uploadVideo`, and `createVideoPost` to `src/clients/linkedin.ts`.**
+
+## Accomplishments
+- `linkedinRestRequest` helper: mirrors `linkedinRequest` but targets `https://api.linkedin.com/rest` with `LinkedIn-Version: 202501` header
+- `uploadVideo(videoUrl, ownerUrn, accessToken)`: 5-step flow — download (ArrayBuffer, 120s timeout), initialize upload, chunk PUT at 4MB each with ETag collection, finalize, poll every 3s up to 90s until `AVAILABLE`
+- `createVideoPost(args, customer)`: resolves token + profile, calls `uploadVideo`, posts via `POST /rest/posts` (not `/v2/ugcPosts`), reads post ID from `x-restli-id` header, wraps in audit log
+
+## Files Created/Modified
+- `src/clients/linkedin.ts` — added ~120 lines after existing `createPost`
+
+## Decisions Made
+- Used inline `fetch` for `POST /rest/posts` to read `x-restli-id` header before body is consumed
+- `void CHUNK_SIZE` line keeps the constant referenced to avoid unused-var lint; actual slice ranges come from `uploadInstructions[].firstByte/lastByte`
+- ETags stripped of surrounding quotes before passing to `finalizeUpload`
+
+## Issues Encountered
+- `redis` and `mysql2` packages were not installed (`node_modules` was missing). Ran `npm install` — build became clean
+
+## Next Step
+Ready for 01-02-PLAN.md