Add job tracking with PostgreSQL, image storage, and review workflow

- Add PostgreSQL service to docker-compose with health check and postgres_data volume
- Mount ./ocr_images as bind volume for persistent image storage
- Add backend/database.py with schema init and get_db() context manager
- Add 5 new API endpoints: POST /api/jobs, GET /api/jobs (search), GET /api/jobs/{id},
  GET /api/jobs/{id}/image, PUT /api/jobs/{id}/review
- Jobs are saved with author/book/chapter/page metadata, auto UUID, and submitted_at timestamp
- Jobs start as 'unreviewed'; review captures edited text, reviewer name, and reviewed_at
- Add MetadataForm.jsx (author/book/chapter/page inputs) to the New Job panel
- Add JobsPanel.jsx with search/filter, paginated list, and detail pane with review form
- Add "Commit Job" button to ResultPanel (plain_ocr mode only) with success/error feedback
- Add "New Job" / "Browse Jobs" navigation to the app header

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

backend/database.py

@@ -0,0 +1,71 @@
+import os
+import psycopg2
+import psycopg2.extras
+from contextlib import contextmanager
+from decouple import config as env_config
+
+DATABASE_URL = env_config(
+    "DATABASE_URL",
+    default="postgresql://ocr_user:ocr_password@postgres:5432/ocr_db"
+)
+
+
+def _get_conn():
+    return psycopg2.connect(DATABASE_URL, cursor_factory=psycopg2.extras.RealDictCursor)
+
+
+def init_db():
+    """Create tables if they don't exist. Called once at startup."""
+    conn = None
+    try:
+        conn = _get_conn()
+        with conn.cursor() as cur:
+            cur.execute("""
+                CREATE TABLE IF NOT EXISTS ocr_jobs (
+                    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+                    author TEXT,
+                    book TEXT,
+                    chapter TEXT,
+                    page TEXT,
+                    submitted_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+                    image_path TEXT NOT NULL,
+                    original_filename TEXT,
+                    ocr_text TEXT,
+                    status TEXT NOT NULL DEFAULT 'unreviewed',
+                    reviewed_text TEXT,
+                    reviewer_name TEXT,
+                    reviewed_at TIMESTAMPTZ,
+                    mode TEXT
+                )
+            """)
+            # Index for fast full-text-style searches on common fields
+            cur.execute("""
+                CREATE INDEX IF NOT EXISTS ocr_jobs_status_idx ON ocr_jobs(status)
+            """)
+            cur.execute("""
+                CREATE INDEX IF NOT EXISTS ocr_jobs_submitted_at_idx ON ocr_jobs(submitted_at DESC)
+            """)
+        conn.commit()
+        print("Database initialized.")
+    except Exception as exc:
+        print(f"Database init failed: {exc}")
+        if conn:
+            conn.rollback()
+        raise
+    finally:
+        if conn:
+            conn.close()
+
+
+@contextmanager
+def get_db():
+    """Yield a connection and auto-commit/rollback."""
+    conn = _get_conn()
+    try:
+        yield conn
+        conn.commit()
+    except Exception:
+        conn.rollback()
+        raise
+    finally:
+        conn.close()