rename: the server is Inkwell — package, env vars, image, compose, export marker

Step 2 of milestone 481. The operator chose a full rename (Scribe note 5071), so
this goes past the display strings into the identities:

- src/thoughtsync → src/inkwell; every import, the Dockerfile and both compose
  commands, alembic env, pyproject
- THOUGHTSYNC_* → INKWELL_* (database URL, secret key, log level, tag/port/bind)
- container data dir /var/thoughtsync → /var/inkwell
- image git.fabledsword.com/bvandeusen/inkwell; Postgres user/db default inkwell;
  CI's integration service follows
- the files the image serves are inkwell.*. fetch-clients.sh still fetches the
  thoughtsync-named release assets, because the lanes that publish them are
  renamed in steps 3 and 4
- exports are written with app "inkwell"

Two deliberate exceptions, both because data rides on them:

- compose volumes are now named explicitly and overridable (INKWELL_DB_VOLUME,
  INKWELL_DATA_VOLUME), so a deployment installed as ThoughtSync points at the
  volumes and DB identity it already has. .env.example says exactly what to set
- import still accepts app "thoughtsync", because exports written before the
  rename are backups. Tested both ways

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

alembic/env.py

@@ -8,8 +8,8 @@ from sqlalchemy.ext.asyncio import async_engine_from_config
 
 from alembic import context
 
-from thoughtsync.models import Base
-import thoughtsync.models.all  # noqa: F401  — registers every model on Base.metadata
+from inkwell.models import Base
+import inkwell.models.all  # noqa: F401  — registers every model on Base.metadata
 
 config = context.config
 
@@ -18,7 +18,7 @@ if config.config_file_name is not None:
 
 config.set_main_option(
     "sqlalchemy.url",
-    os.environ.get("THOUGHTSYNC_DATABASE_URL", config.get_main_option("sqlalchemy.url")),
+    os.environ.get("INKWELL_DATABASE_URL", config.get_main_option("sqlalchemy.url")),
 )
 
 target_metadata = Base.metadata