Add PDF/HEIC/image upload support and improve receipt extraction

- Add backend image conversion endpoint (POST /api/convert-image) supporting
  PDF, HEIC, PNG, WebP via Pillow, PyMuPDF, and pillow-heif
- Add separate "Upload file" button in UI while keeping camera-first behavior
  for the photo area and + button
- Improve Haiku extraction prompt for hotel receipts (parenthesized total)
- Increase max image resolution from 1024px to 2048px for better OCR accuracy
- Add libheif-dev system dependency in Dockerfile

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

receipts.html

@@ -542,6 +542,8 @@
         <span>Tap to take photo</span>
       </div>
       <input type="file" id="photo-input" accept="image/*" capture="environment" hidden>
+      <input type="file" id="file-input" accept="image/*,.pdf,.heic,.heif,application/pdf" hidden>
+      <button type="button" id="upload-file-btn" style="margin-top:8px;width:100%;padding:10px;border:1.5px dashed #aaa;border-radius:8px;background:#fafafa;color:#666;font-size:0.9rem;cursor:pointer;">Upload file (PDF, HEIC, image)</button>
       <div class="extract-status" id="extract-status"></div>
     </div>
 
@@ -695,6 +697,8 @@
   const modalTitle = document.getElementById("modal-title");
   const photoArea = document.getElementById("photo-area");
   const photoInput = document.getElementById("photo-input");
+  const fileInput = document.getElementById("file-input");
+  const uploadFileBtn = document.getElementById("upload-file-btn");
   const dateInput = document.getElementById("date-input");
   const amountInput = document.getElementById("amount-input");
   const categoryInput = document.getElementById("category-input");
@@ -866,6 +870,7 @@
   function closeModal() {
     overlay.classList.remove("open");
     photoInput.value = "";
+    fileInput.value = "";
   }
 
   function updatePhotoArea() {
@@ -876,7 +881,7 @@
       photoArea.classList.remove("has-photo");
       photoArea.innerHTML = `
         <svg width="32" height="32" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5"><path d="M23 19a2 2 0 01-2 2H3a2 2 0 01-2-2V8a2 2 0 012-2h4l2-3h6l2 3h4a2 2 0 012 2z"/><circle cx="12" cy="13" r="4"/></svg>
-        <span>Tap to take photo</span>`;
+        <span>Tap to add photo or file</span>`;
     }
   }
 
@@ -1055,6 +1060,7 @@
   });
 
   photoArea.addEventListener("click", () => photoInput.click());
+  uploadFileBtn.addEventListener("click", () => fileInput.click());
 
   // --- Receipt extraction via Claude ---
   const extractStatus = document.getElementById("extract-status");
@@ -1290,11 +1296,50 @@
     }, "image/jpeg", 0.85);
   });
 
+  async function convertViaBackend(file) {
+    const buf = await file.arrayBuffer();
+    const r = await fetch("/api/convert-image", {
+      method: "POST",
+      headers: { "Content-Type": file.type || "application/octet-stream" },
+      body: buf
+    });
+    if (!r.ok) throw new Error("Conversion failed");
+    return await r.blob();
+  }
+
+  function needsBackendConversion(file) {
+    const type = (file.type || "").toLowerCase();
+    const name = (file.name || "").toLowerCase();
+    if (type === "application/pdf" || name.endsWith(".pdf")) return true;
+    if (type === "image/heic" || type === "image/heif" || name.endsWith(".heic") || name.endsWith(".heif")) return true;
+    return false;
+  }
+
   photoInput.addEventListener("change", async e => {
     const file = e.target.files[0];
     if (!file) return;
-    const resized = await resizeImage(file, 1024);
-    openCropOverlay(resized);
+    const blob = await resizeImage(file, 2048);
+    openCropOverlay(blob);
+  });
+
+  fileInput.addEventListener("change", async e => {
+    const file = e.target.files[0];
+    if (!file) return;
+    let blob;
+    if (needsBackendConversion(file)) {
+      try {
+        extractStatus.textContent = "Converting file...";
+        blob = await convertViaBackend(file);
+      } catch (err) {
+        extractStatus.textContent = "Conversion failed";
+        return;
+      } finally {
+        if (extractStatus.textContent === "Converting file...") extractStatus.textContent = "";
+      }
+    } else {
+      blob = await resizeImage(file, 2048);
+    }
+    openCropOverlay(blob);
   });
 
   btnSave.addEventListener("click", async () => {