release: 1.9.3: Panel-redesign prep: mockups, routes, design contract (docs only)

Panel-redesign prep, docs only: stage 1-2 mockups on all 33 screens, the accepted header/type-scale/contrast corrections, the account e-mail and inbound-delegation decisions, and the routes/quarantine/preflight roadmap screens. Nothing in `internal/web` changes; the design stays `candidate` (3/21) until the redesign itself ships as `2.0.0`.
Added:
  - Panel redesign, account e-mail and notifications: a user's e-mail is its own
  - Panel redesign, contrast: a sweep of every text node against its real ground
  - Panel redesign, header (owner's choice: variant A, with the perforation on a
  - Panel redesign, type scale: about 40 % of the panel's text measured under
  - Panel redesign, header comparison sheet
  … (8 more in CHANGELOG)

Full detail: CHANGELOG.md (1.9.3).

docs/guide.md

@@ -173,7 +173,7 @@ cat ./data/setup-token
 #### Fixed image tag
 
 `deploy/docker-compose.yml` pins an explicit version (`ghcr.io/mixeme/selfpost:X.Y.Z`),
-deliberately never `:latest`. The current pin is `1.9.2`. Intermediate
+deliberately never `:latest`. The current pin is `1.9.3`. Intermediate
 CHANGELOG sections (`0.2.0`…`0.6.0`) record development cuts from before that
 image was published. Pinning matters because of the backup version check (see
 [Full backup and restore](#full-backup-and-restore)): the panel binary's