Speed up property model viewer: on-demand rendering, shared UGC caches, validators and gzip (#134)

* Speed up property model viewer loading

- Render the viewer on demand (load completion, camera change, resize)
  instead of every animation frame
- Share the UGC brick geometry cache and parsed Materials.xml across all
  UGC models on the converter
- Serve model and ldddb files with strong ETag/Last-Modified validators
  and conditional requests so repeat visits get 304s
- Gzip model and ldddb responses (COMPRESS_MODEL_RESPONSES), optionally
  storing .gz copies on disk (CACHE_COMPRESSED_MODELS)

Co-authored-by: HailStorm32 <demetriv.s.7@gmail.com>

* Add configurable redraw behaviour while property models load

PROPERTY_VIEWER_LOAD_REDRAW ('none' or 'interval') and
PROPERTY_VIEWER_REDRAW_INTERVAL_MS control whether the property viewer
redraws as individual models finish loading. A final draw always happens
once all loads complete or fail, and a loading indicator is shown
meanwhile. Also wrap long lines added by this branch for flake8.

Co-authored-by: HailStorm32 <demetriv.s.7@gmail.com>

* Show model loading progress in the property viewer

Replace the static 'Loading models...' badge in the upper-left corner with
a progress indicator, e.g. 'Loading models: 42% (89/203)', counting loaded
and failed models out of the total. When everything is done it shows
'Loaded 100% (203/203)' (with '(N failed)' if any), turns green (orange on
failures) and fades to a faint badge after a few seconds.

The indicator is a DOM element updated at most once per animation frame,
so it does not trigger canvas redraws in either redraw mode.

Co-authored-by: HailStorm32 <demetriv.s.7@gmail.com>

* Make the loading progress badge more opaque and readable

Use a ~93% opaque background for all states (dark while loading, darker
green when done, orange on failures), bold white text with a subtle text
shadow, border and drop shadow, and only fade to 70% opacity after
completion so it stays legible over colourful models.

Co-authored-by: HailStorm32 <demetriv.s.7@gmail.com>

* Batch UGC models and load the viewer's brick data asynchronously

Brick-built (UGC) models used to be loaded with synchronous XHRs on the
main thread: one request per model's LXFML plus one per brick primitive
file, strictly one after another, with the page frozen meanwhile. On a
remote server every request costs a network round trip, so a property
with 654 UGC models took about two minutes to load.

- New route properties.get_ugc_models/<property id> (login required, like
  get_model) returns all UGC LXFML of a property as one JSON object
  ({content id: lxfml}) from a single DB query. It is gzip-encoded per
  COMPRESS_MODEL_RESPONSES and has an ETag over the whole set, so repeat
  loads get a 304. The per-model get_model route keeps working.
- The viewer lists the brick database, fetches the LXFML (batched on
  view_models, per model with bounded concurrency otherwise) and then each
  needed brick primitive exactly once with at most 8 requests in flight,
  all with async fetch. Meshes are then built in short slices so the page
  stays responsive. The progress badge counts brick-built models as they
  are built and shows the fetch stage (e.g. 'bricks 120/385').
- Loading finishes once both the loading manager (pre-built models,
  ground texture) and the brick-built models are done; redraw modes are
  unchanged ('none' draws once at the end, 'interval' at most every N ms).
- get_model for a UGC model only decompresses the LXFML when it has to
  send a body (a matching If-None-Match skips it).

Co-authored-by: HailStorm32 <demetriv.s.7@gmail.com>

* Show the prebuilt material stage on the loading badge

While prebuilt models load, the badge now shows how many MTL files have
arrived (e.g. 'materials 120/203'), so progress moves from the start on
prebuilt-heavy properties instead of sitting at 0% until the first OBJ
loads.

Co-authored-by: HailStorm32 <demetriv.s.7@gmail.com>

* Show a rendering state on the badge before the final render

The final full render can block the main thread for a second or more on
large properties, which made the badge look frozen. Once all loads are
done the badge now shows 'Rendering N parts…' with a CSS spinner (a
transform animation the compositor keeps running), waits two animation
frames so it is painted, then renders and shows the Loaded state.

Co-authored-by: HailStorm32 <demetriv.s.7@gmail.com>

---------

Co-authored-by: bob-g-code <346622190+bob-g-code@users.noreply.github.com>
Co-authored-by: HailStorm32 <demetriv.s.7@gmail.com>

app/__init__.py

@@ -10,6 +10,7 @@ from flask_user import user_registered, current_user, user_logged_in
 from flask_wtf.csrf import CSRFProtect
 from flask_apscheduler import APScheduler
 from app.luclient import register_luclient_jinja_helpers
+from app.compressed_files import register_compressed_files
 import pathlib
 import shutil
 import stat
@@ -111,6 +112,7 @@ def create_app():
 
     register_logging(app)
     register_settings(app)
+    register_compressed_files(app)
     register_extensions(app)
     register_blueprints(app)
     register_luclient_jinja_helpers(app)
@@ -365,6 +367,26 @@ def register_settings(app):
         app.config['ENABLE_CHAR_XML_UPLOAD']
     )
 
+    # Property model viewer compression (see settings_example.py)
+    for key, default in (
+        ("COMPRESS_MODEL_RESPONSES", True), ("CACHE_COMPRESSED_MODELS", False)
+    ):
+        value = os.getenv(key, app.config.get(key, default))
+        if isinstance(value, str):
+            value = value.strip().lower() in ("1", "true", "yes", "on")
+        app.config[key] = bool(value)
+
+    # Property model viewer redraw while models load (see settings_example.py)
+    key = "PROPERTY_VIEWER_LOAD_REDRAW"
+    redraw = str(os.getenv(key, app.config.get(key, "none"))).strip().lower()
+    app.config[key] = redraw if redraw in ("none", "interval") else "none"
+    key = "PROPERTY_VIEWER_REDRAW_INTERVAL_MS"
+    try:
+        interval = int(os.getenv(key, app.config.get(key, 500)))
+    except (TypeError, ValueError):
+        interval = 500
+    app.config[key] = max(interval, 16)
+
     if "CLIENT_LOCATION" not in app.config:
         app.config['CLIENT_LOCATION'] = 'app/luclient/'
     app.config['CLIENT_LOCATION'] = os.getenv(