fix: Docker entrypoint arg handling + configurable model directory

Fixes #384: docker run with --source/--tick-ms flags now works correctly.
Fixes #399: model files in mounted volumes are now discoverable via MODELS_DIR env var.

Root cause (issue #384):
The Dockerfile used ENTRYPOINT ["/bin/sh", "-c"] with a shell-form CMD.
When users passed flags like `--source wifi --tick-ms 500` as docker run
arguments, Docker replaced CMD entirely, resulting in
`/bin/sh -c "--source wifi --tick-ms 500"` which executes `--source` as
a shell command → `--source: not found`.

Root cause (issue #399):
Model directory was hardcoded to the relative path `data/models`. When Docker
users mounted models to `/app/models/`, the scan looked in the wrong place.

Changes:

1. docker/docker-entrypoint.sh (new):
   - Proper entrypoint script that handles both env-var-based defaults and
     user-passed CLI flags
   - No arguments → starts server with CSI_SOURCE env var as --source
   - Flag arguments (start with -) → prepends /app/sensing-server + defaults,
     appends user flags (clap last-wins allows overrides)
   - Non-flag first arg → exec passthrough (e.g., /bin/sh for debugging)
   - Sets --bind-addr 0.0.0.0 (was 127.0.0.1 which blocks container access)

2. docker/Dockerfile.rust:
   - Switch from ENTRYPOINT ["/bin/sh", "-c"] to exec-form entrypoint
   - Add MODELS_DIR env var (default: data/models)
   - COPY the entrypoint script into the image

3. docker/docker-compose.yml:
   - Remove shell-form command (entrypoint handles defaults)
   - Add MODELS_DIR env var

4. model_manager.rs + main.rs:
   - Replace hardcoded `data/models` path with `effective_models_dir()`
     / `models_dir()` that reads MODELS_DIR env var at runtime
   - Docker users can now: docker run -v /host/models:/app/models -e MODELS_DIR=/app/models

5. tests/test_docker_entrypoint.sh (new, 17 tests):
   - Default CSI_SOURCE substitution (6 assertions)
   - Custom CSI_SOURCE propagation
   - User-passed flag arguments (--source, --tick-ms, --model)
   - Unset CSI_SOURCE defaults to auto
   - Explicit command passthrough
   - MODELS_DIR env var propagation

rust-port/wifi-densepose-rs/crates/wifi-densepose-sensing-server/src/main.rs

@@ -2797,7 +2797,7 @@ async fn delete_model(
     if safe_id.is_empty() || safe_id != id {
         return Json(serde_json::json!({ "error": "invalid model id", "success": false }));
     }
-    let path = PathBuf::from("data/models").join(format!("{}.rvf", safe_id));
+    let path = effective_models_dir().join(format!("{}.rvf", safe_id));
     if path.exists() {
         if let Err(e) = std::fs::remove_file(&path) {
             warn!("Failed to delete model file {:?}: {}", path, e);
@@ -2842,9 +2842,18 @@ async fn activate_lora_profile(
     Json(serde_json::json!({ "success": true, "profile": profile }))
 }
 
-/// Scan `data/models/` for `.rvf` files and return metadata.
+/// Return the effective models directory, respecting the `MODELS_DIR`
+/// environment variable.  Defaults to `data/models`.
+fn effective_models_dir() -> PathBuf {
+    PathBuf::from(
+        std::env::var("MODELS_DIR").unwrap_or_else(|_| "data/models".to_string()),
+    )
+}
+
+/// Scan the models directory for `.rvf` files and return metadata.
+/// Respects the `MODELS_DIR` environment variable.
 fn scan_model_files() -> Vec<serde_json::Value> {
-    let dir = PathBuf::from("data/models");
+    let dir = effective_models_dir();
     let mut models = Vec::new();
     if let Ok(entries) = std::fs::read_dir(&dir) {
         for entry in entries.flatten() {
@@ -2874,9 +2883,10 @@ fn scan_model_files() -> Vec<serde_json::Value> {
     models
 }
 
-/// Scan `data/models/` for `.lora.json` LoRA profile files.
+/// Scan the models directory for `.lora.json` LoRA profile files.
+/// Respects the `MODELS_DIR` environment variable.
 fn scan_lora_profiles() -> Vec<serde_json::Value> {
-    let dir = PathBuf::from("data/models");
+    let dir = effective_models_dir();
     let mut profiles = Vec::new();
     if let Ok(entries) = std::fs::read_dir(&dir) {
         for entry in entries.flatten() {
@@ -4604,7 +4614,8 @@ async fn main() {
     }
 
     // Ensure data directories exist for models and recordings
-    let _ = std::fs::create_dir_all("data/models");
+    let models_dir = effective_models_dir();
+    let _ = std::fs::create_dir_all(&models_dir);
     let _ = std::fs::create_dir_all("data/recordings");
 
     // Discover model and recording files on startup

rust-port/wifi-densepose-rs/crates/wifi-densepose-sensing-server/src/model_manager.rs

@@ -30,8 +30,19 @@ use crate::rvf_container::RvfReader;
 
 // ── Models data directory ────────────────────────────────────────────────────
 
-/// Base directory for RVF model files.
-pub const MODELS_DIR: &str = "data/models";
+/// Default base directory for RVF model files.
+///
+/// Overridden at runtime by the `MODELS_DIR` environment variable so that
+/// Docker users can point to a mounted volume without rebuilding:
+///   docker run -v /path/to/models:/app/models -e MODELS_DIR=/app/models ...
+pub const MODELS_DIR_DEFAULT: &str = "data/models";
+
+/// Return the effective models directory, respecting `MODELS_DIR` env var.
+pub fn models_dir() -> PathBuf {
+    PathBuf::from(
+        std::env::var("MODELS_DIR").unwrap_or_else(|_| MODELS_DIR_DEFAULT.to_string()),
+    )
+}
 
 // ── Types ────────────────────────────────────────────────────────────────────
 
@@ -110,7 +121,7 @@ pub type AppState = Arc<RwLock<super::AppStateInner>>;
 
 /// Scan the models directory and build `ModelInfo` for each `.rvf` file.
 async fn scan_models() -> Vec<ModelInfo> {
-    let dir = PathBuf::from(MODELS_DIR);
+    let dir = models_dir();
     let mut models = Vec::new();
 
     let mut entries = match tokio::fs::read_dir(&dir).await {
@@ -204,7 +215,7 @@ async fn scan_models() -> Vec<ModelInfo> {
 
 /// Load a model from disk by ID and return its `LoadedModelState`.
 fn load_model_from_disk(model_id: &str) -> Result<LoadedModelState, String> {
-    let file_path = PathBuf::from(MODELS_DIR).join(format!("{model_id}.rvf"));
+    let file_path = models_dir().join(format!("{model_id}.rvf"));
     let reader = RvfReader::from_file(&file_path)?;
 
     let manifest = reader.manifest().unwrap_or_default();