docs: drop stale chromadb-setup.md; strip broken VM-102 frontmatter

Second pass on docs/ cleanup (item #15 in STATUS.md):

- pfi/chromadb-setup.md: deleted. References configs/pfi-ana/... and
  scripts/setup-chromadb.sh, neither of which exist in this repo
  (artifacts of an earlier project layout). ChromaDB is already live
  per docker-stack.md; the operational truth lives there.
- pfi/docker-stack.md: removed the cross-link to the deleted file and
  pulled the bit of useful content from it (auth-token generation +
  client Settings example) into the inline ChromaDB section.
- pfi/vm-102-matrix-{synapse,appservice}.md: stripped the YAML
  frontmatter. The `path:` values pointed at docs/pfi-ana/... which
  doesn't exist in this repo; no toolchain consumed the metadata.
- README.md: tree updated to reflect the deletion.

VM-102 docs kept separate by design — each is right-sized; merging
would push past the ~500-line guideline.

docs/pfi/vm-102-matrix-synapse.md

@@ -1,18 +1,3 @@
----
-id: vm-102-matrix-synapse
-title: "VM 102 — Matrix Synapse Deployment"
-summary: "Docker deployment of Synapse homeserver with PostgreSQL and Element Web on VM 102 (PFI-ANA-Docker). Covers compose file, configuration, storage paths, and admin setup."
-tags: ["infrastructure", "pfi", "pfi-ana", "matrix", "docker", "vm-102", "synapse", "self-hosted", "deployment"]
-keywords: ["matrix.pfi.local", "synapse", "element-web", "10.250.50.70", "VM-102", "PFI-ANA-Docker", "postgres:16", "appservice", "AIPA"]
-links:
-  - "[Matrix Protocol Reference](../Infrastructure-PFI-Project-Index.md)"
-  - "[VM-102 Proxmox Config](../../../configs/pfi-ana/proxmox/vm-102.conf)"
-  - "[Docker Stack Conventions](docker-stack.md)"
-created: 2026-04-11T00:00:00+00:00
-modified: 2026-04-11T00:00:00+00:00
-path: docs/pfi-ana/vm-102-matrix-synapse.md
----
-
 # VM 102 — Matrix Synapse Deployment
 
 ## Overview