feat(session): per-owner printer/config storage via cookie-scoped bearer key

Printers and groups (Client) are now scoped to an Owner identified by an opaque
bearer key (secrets.token_urlsafe(32)) stored in an httponly cookie, defaulting
to temporary. First-visit modal offers backup-key download (marks permanent) or
temporary-only choice. /session/restore re-attaches a fresh browser to a saved
key. Every printer-facing route enforces ownership (404 on mismatch, not just
filtering) since printer IDs are sequential ints. Drivers stay global/shared.

On upgrade, pre-existing printer/client rows backfill to a synthetic legacy Owner;
its key is written to {DATA_DIR}/legacy_owner_key.txt for manual restore.

SECURITY: Added Origin/Referer same-origin check on POST /session/restore to
block login-CSRF/session-fixation attacks (cross-site form POST can't re-point
victim's cookie at attacker's Owner without hitting that check first).

Tests: 140 pass (2 deselected: pre-existing locale-flaky, unrelated to this change).
Verified live: modal on first visit, isolation between browsers, backup-key
download and restore flow work end-to-end.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -14,6 +14,7 @@ pytest tests/ -k "test_name"          # single test by name
 **Run dev server:**
 ```bash
 export DATA_DIR=/tmp/imptune_data
+export COOKIE_SECURE=false  # plain HTTP — omit if serving behind TLS
 uvicorn imptune.main:app --reload --port 8000
 ```
 
@@ -33,18 +34,21 @@ pip install -r requirements.txt -r requirements-dev.txt
 ImpTune make printer deploy packages (`.intunewin` for Intune, `.zip` for NinjaRMM) from Windows driver ZIPs + web UI. No external services — single FastAPI + SQLite + Docker volume.
 
 **Request flow:**
-1. Driver upload → `api/drivers.py` → `services/inf_parser.py` parse INF → `storage/driver_store.py` store by SHA256 → Peewee `Driver` record
-2. Printer config → `api/printers.py` → `db/models.py` `Printer` record (links Driver FK)
+1. Driver upload → `api/drivers.py` → `services/inf_parser.py` parse INF → `storage/driver_store.py` store by SHA256 → Peewee `Driver` record (shared/global — visible to every Owner)
+2. Printer config → `api/printers.py` → `db/models.py` `Printer` record (links Driver FK, scoped to `request.state.owner`)
 3. Icon upload → `api/icons.py` → Pillow validate PNG 256×256 → SHA256 storage → `Icon` record
 4. Package export → `api/packages.py` → `generators/script_generator.py` render Jinja2 PS1 templates → `generators/intunewin_builder.py` encrypt ZIP (AES-256-CBC + HMAC-SHA256)
 
 **Key modules:**
-- `imptune/config.py` — `DATA_DIR`, `DB_PATH`, `DRIVERS_DIR`, `ICONS_DIR` from env
-- `imptune/db/database.py` — SQLite WAL mode + `foreign_keys=1`; all models inherit `BaseModel`
+- `imptune/config.py` — `DATA_DIR`, `DB_PATH`, `DRIVERS_DIR`, `ICONS_DIR`, `COOKIE_SECURE` from env
+- `imptune/db/database.py` — SQLite WAL mode + `foreign_keys=1`; all models inherit `BaseModel`; `init_db()` also backfills `owner_id` on pre-per-owner-scoping DBs into a synthetic legacy `Owner` (key written to `{DATA_DIR}/legacy_owner_key.txt`)
+- `imptune/services/session.py` — `OwnerSessionMiddleware` resolves `request.state.owner` from the `imptune_owner_key` cookie, creating one on first visit (skips `/health`)
 - `imptune/services/inf_parser.py` — auto-detect encoding (UTF-16/UTF-8/cp1252), resolve `%TOKEN%` from `[Strings]`, handle multi-model INFs
 - `imptune/generators/intunewin_builder.py` — Python-native `.intunewin` (ZIP-in-ZIP); IV 16 bytes (not 32); match reference tool `1.8.6.0` output
 - `imptune/templates/scripts/` — Jinja2 templates for `install.ps1`, `uninstall.ps1`, `detect.ps1`
 
+**Per-owner storage:** `Printer`/`Client` (groups) are scoped to an `Owner` identified by an opaque bearer key in a cookie — no accounts. `Driver` stays global/shared. Every route taking a `printer_id`/`client_id` must filter/check `.owner == request.state.owner` (404, not 403, on mismatch) — printer IDs are small sequential ints, so a list-only filter isn't enough. Onboarding modal (`templates/base.html`, gated on `request.state.is_new_owner`) offers "download backup key" (`GET /session/key/download`, marks `Owner.is_permanent`) vs. temporary; `/session/restore` re-attaches a browser to a previously downloaded key. In tests, use the `owner` fixture (`tests/conftest.py`) when creating `Printer`/`Client` rows directly via the ORM so the `client` fixture's cookie-scoped requests can see them.
+
 **UI stack:** Pico CSS + HTMX 2 + Alpine.js 3 + Jinja2 server-side templates.
 
 **HTMX pattern:** Forms `hx-post`, swap `#driver-list` / `#printer-list` / `#client-list` targets. Errors return inline HTML fragments (HTTP 400/409) via `_error_response()`. Success return partials from `templates/partials/`.
@@ -64,4 +68,5 @@ ImpTune make printer deploy packages (`.intunewin` for Intune, `.zip` for NinjaR
 | Var | Default | Purpose |
 |-----|---------|---------|
 | `DATA_DIR` | `/data` | Storage root (DB + drivers + icons) |
-| `PORT` | `8000` | Server port |
+| `PORT` | `8000` | Server port |
+| `COOKIE_SECURE` | `true` | Owner-session cookie `Secure` flag. Set `false` for local plain-HTTP dev (`uvicorn --reload`) or the browser drops the cookie and a new Owner is created on every request. |