feat: replace Cancel with Pause/Resume — survives server restarts

- scanner.py: replace cancel_requested with pause_requested throughout;
  pause during walk drains in-flight futures gracefully then saves state;
  phash phase processes in 500-image chunks with pause check between each;
  _save_pause_state() persists files_indexed/phashes_done/last_phase to DB;
  init_db() already detects killed-mid-scan (running→paused) on startup

- main.py: add POST /api/scan/pause and POST /api/scan/resume endpoints;
  /api/scan/cancel kept as alias; scan_status now returns folder_path,
  files_indexed, phashes_done; scan_reset clears all new fields

- index.html: "Cancel" → "⏸ Pause" button; new #paused-area banner shows
  folder, files indexed, phashes done with "▶ Resume" and "Full reset"
  buttons; updateScanUI handles paused status; pauseScan()/resumeScan()
  JS functions added; chip gains .paused amber style

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/main.py

@@ -105,11 +105,14 @@ def scan_start(body: ScanStartBody):
     sc.scan_state.update(
         scan_id=scan_id,
         status="running",
-        phase="discovery",
+        phase="takeout",
         progress=0,
         total=0,
         message="Starting...",
-        cancel_requested=False,
+        pause_requested=False,
+        files_indexed=0,
+        phashes_done=0,
+        folder_path=body.folder_path,
         stats={},
     )
 
@@ -146,24 +149,76 @@ def scan_status():
     con.close()
 
     return {
-        "scan_id": state["scan_id"],
-        "status": state["status"],
-        "phase": state["phase"],
-        "progress": state["progress"],
-        "total": state["total"],
-        "message": state["message"],
-        "stats": stats,
+        "scan_id":      state["scan_id"],
+        "status":       state["status"],
+        "phase":        state["phase"],
+        "progress":     state["progress"],
+        "total":        state["total"],
+        "message":      state["message"],
+        "folder_path":  state.get("folder_path"),
+        "files_indexed": state.get("files_indexed", 0),
+        "phashes_done": state.get("phashes_done", 0),
+        "stats":        stats,
     }
 
 
-@app.post("/api/scan/cancel")
-def scan_cancel():
+@app.post("/api/scan/pause")
+def scan_pause():
     if sc.scan_state["status"] != "running":
         raise HTTPException(400, "No scan is currently running")
-    sc.scan_state["cancel_requested"] = True
+    sc.scan_state["pause_requested"] = True
     return {"success": True}
 
 
+# Keep /cancel as an alias so any lingering clients still work
+@app.post("/api/scan/cancel")
+def scan_cancel():
+    return scan_pause()
+
+
+@app.post("/api/scan/resume")
+def scan_resume():
+    if sc.scan_state["status"] != "paused":
+        raise HTTPException(400, "No paused scan to resume")
+
+    folder_path = sc.scan_state.get("folder_path")
+    if not folder_path:
+        raise HTTPException(400, "No folder path saved — please start a new scan")
+
+    con = get_db()
+    cur = con.cursor()
+    cur.execute(
+        "INSERT INTO scans (folder_path, status) VALUES (?, 'running')",
+        (folder_path,),
+    )
+    scan_id = cur.lastrowid
+    con.commit()
+    con.close()
+
+    sc.scan_state.update(
+        scan_id=scan_id,
+        status="running",
+        phase="takeout",
+        progress=0,
+        total=0,
+        message="Resuming scan...",
+        pause_requested=False,
+        files_indexed=0,
+        phashes_done=0,
+        folder_path=folder_path,
+        stats={},
+    )
+
+    thread = threading.Thread(
+        target=sc.run_scan,
+        args=(folder_path, scan_id, "incremental"),
+        daemon=True,
+    )
+    thread.start()
+
+    return {"scan_id": scan_id}
+
+
 @app.delete("/api/scan/reset")
 def scan_reset(confirm: str = Query("")):
     if confirm != "RESET":
@@ -178,7 +233,9 @@ def scan_reset(confirm: str = Query("")):
     con.close()
     sc.scan_state.update(
         scan_id=None, status="idle", phase="idle",
-        progress=0, total=0, message="", stats={},
+        progress=0, total=0, message="",
+        pause_requested=False, files_indexed=0,
+        phashes_done=0, folder_path=None, stats={},
     )
     return {"success": True}