rename: the docs say Inkwell, and nothing else still says ThoughtSync by accident

Step 6 of milestone 481. README, docs/*, ci-requirements.md, the desktop and
Arch READMEs, alembic.ini, .gitignore, the frontend package name, the service
worker's cache name (its activate handler deletes any cache by another name, so
the old one is cleaned up), and the Android names in the release body.

What still says thoughtsync does so on purpose (Scribe note 5071):
- the desktop data crossover (crossover.rs) and its startup log
- the old-export import marker
- the "Upgrading from ThoughtSync" block in .env.example, and compose's pointer
  to it
- the packages being retired: deb conflicts/replaces thought-sync, pacman
  thoughtsync and thoughtsync-desktop
- the Android signing keyAlias, which names a key in the existing keystore
- history: shipped alembic migrations, and the test-binary hashes that
  ci-requirements.md records from 2026-08-18

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -1,4 +1,4 @@
-# ThoughtSync
+# Inkwell
 
 Self-hosted personal thought-capture web app in the **FabledSword** family — a
 Google-Keep-style **masonry post-it board** for capturing disparate thoughts in
@@ -23,7 +23,7 @@ docker-compose.yml   local app + Postgres stack
 
 ## Development
 
-Backend (needs a Postgres reachable at `THOUGHTSYNC_DATABASE_URL`):
+Backend (needs a Postgres reachable at `INKWELL_DATABASE_URL`):
 
 ```sh
 pip install -e ".[dev]"
@@ -64,40 +64,40 @@ services:
     image: postgres:16-alpine
     restart: unless-stopped
     environment:
-      POSTGRES_USER: thoughtsync
+      POSTGRES_USER: inkwell
       POSTGRES_PASSWORD: CHANGE_ME          # change this
-      POSTGRES_DB: thoughtsync
+      POSTGRES_DB: inkwell
     volumes:
-      - thoughtsync-db:/var/lib/postgresql/data
+      - inkwell-db:/var/lib/postgresql/data
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U thoughtsync"]
+      test: ["CMD-SHELL", "pg_isready -U inkwell"]
       interval: 5s
       timeout: 5s
       retries: 10
 
   app:
-    image: git.fabledsword.com/bvandeusen/thoughtsync:latest   # :dev for the current dev build
+    image: git.fabledsword.com/bvandeusen/inkwell:latest   # :dev for the current dev build
     restart: unless-stopped
     depends_on:
       db:
         condition: service_healthy
     environment:
-      THOUGHTSYNC_DATABASE_URL: postgresql+asyncpg://thoughtsync:CHANGE_ME@db:5432/thoughtsync
+      INKWELL_DATABASE_URL: postgresql+asyncpg://inkwell:CHANGE_ME@db:5432/inkwell
     volumes:
-      - thoughtsync-data:/var/thoughtsync   # uploaded images; omit if you don't use attachments
+      - inkwell-data:/var/inkwell   # uploaded images; omit if you don't use attachments
     ports:
       - "5000:5000"
 
 volumes:
-  thoughtsync-db:
-  thoughtsync-data:
+  inkwell-db:
+  inkwell-data:
 ```
 
 Then open `http://<host>:5000` and register — **the first account becomes the admin**.
 
-- **Only `THOUGHTSYNC_DATABASE_URL` is required.** `THOUGHTSYNC_SECRET_KEY` is optional; if
+- **Only `INKWELL_DATABASE_URL` is required.** `INKWELL_SECRET_KEY` is optional; if
   unset, a signing key is generated and persisted in the database (sessions survive restarts).
-- Uploaded images live under the `thoughtsync-data` volume at `/var/thoughtsync`.
+- Uploaded images live under the `inkwell-data` volume at `/var/inkwell`.
 - The app waits for the database and runs migrations (`alembic upgrade head`) automatically on start.
 - **Image tags:** `:latest` (stable, built from `main`) · `:dev` (latest `dev`
   build) · `:<git-sha>` on `main` only (immutable, the rollback unit). There are
@@ -108,7 +108,7 @@ Then open `http://<host>:5000` and register — **the first account becomes the
   port, and back up the attachment volume as well as the database. See
   [docs/public-hosting.md](docs/public-hosting.md), which also lists what the app
   hardens on its own and what it deliberately doesn't.
-- **Install as an app (PWA):** ThoughtSync is installable ("Add to Home Screen" / the
+- **Install as an app (PWA):** Inkwell is installable ("Add to Home Screen" / the
   browser's install button) for an app-like window. Browsers only offer install over a
   **secure context**, so put the app behind a reverse proxy terminating **HTTPS** (or reach
   it via `localhost`) — plain `http://<host>:5000` won't show the install prompt.