fix: resolve model weight paths against DATA_DIR (REQ-187)

- config.py: resolve_data_path (legacy abs + rel) + rel_data_path
- all file-opening reads wrapped: preview, autolabel, training, model
  download, live count, projects.get; training_start_point hack replaced
- new writes store paths relative to data/
- legacy stale rows (/home/asus/reTraining/...) resolve without migration
- requirements: REQ-187 added; REQ-188 (per-class max box) + REQ-186
  copy-line amendment drafted for the next task

docs/requirements.md

@@ -139,12 +139,21 @@ changes.
   again. The preview and the batch job still use the same thresholds and per-class overrides.
 - **REQ-186** — The auto-annotate parameters table has a **copy button** that puts every
   selected class's effective settings on the clipboard as short text, one class per line:
-  `class <name> conf <v> iou <v> minbox <v> container <true|false>`. Effective means the
-  per-class override where one is set, otherwise the global slider value; `container` is
-  the class's current checkbox state. The button sits in the shared per-class table, so it
-  exists in both the per-batch auto-annotate modal and the mass (batches tab) modal, and
-  the copied text is a plain baseline for later tuning — no structure beyond the line
-  format. Copying needs no network round-trip and never changes any setting.
+  `class <name> conf <v> iou <v> minbox <v> maxbox <v> container <true|false>`. Effective
+  means the per-class override where one is set, otherwise the global slider value;
+  `container` is the class's current checkbox state. The button sits in the shared
+  per-class table, so it exists in both the per-batch auto-annotate modal and the mass
+  (batches tab) modal, and the copied text is a plain baseline for later tuning — no
+  structure beyond the line format. Copying needs no network round-trip and never changes
+  any setting. (Amended by REQ-188: `maxbox` added to the line.)
+
+- **REQ-188** — Auto-annotation accepts a per-class **maximum box fraction**
+  (`max_box_frac`, default `1.0` = off) beside the existing minimum override of REQ-181:
+  a detection whose area exceeds that fraction of the frame is dropped for that class.
+  It applies everywhere the minimum box fraction applies today (preview, batch job,
+  review assist filter), surfaces as `MaxBox` in the params table, and is included in the
+  REQ-186 copy line. Size bounds are ordinary per-class tuning: the `container` flag
+  (REQ-184) stays purely the NMS containment carve-out and gains no size semantics.
 
 ## E. Review & correction
 
@@ -415,3 +424,10 @@ changes.
 - **REQ-074** — The system writes nothing of its own into the user's video archive folder:
   no outputs, moves, renames or deletions; only user-initiated uploads and folder creation
   (REQ-178) append to it.
+- **REQ-187** — Model weight paths stored in the database (`model_versions.weights_path`,
+  `model_versions.parent_model_path`, `projects.base_model_path`) are **relative to the
+  data directory** when the file lives inside it, and every read resolves them against
+  `DATA_DIR` first. Legacy absolute paths from an older install keep resolving (the data
+  folder has moved once already and everything in it must survive the next move), which
+  strengthens the never-hardcoded rule of REQ-072. Training, preview, the batch job, model
+  download and live counting all reach the same weights through this one resolution.