[FEAT] Clarify the way users must input resources

tabs/tab1_inputs.py

@@ -119,7 +119,7 @@ def dialog_add_custom_resource(cost_sliders, edit_index: int | None = None, pres
     st.markdown('<p class="dialog-title">2 — Available quantity</p>', unsafe_allow_html=True)
 
     batch_amount = st.number_input(
-        f"Available amount ({unit})",
+        label=f"Available amount ({unit})",
         min_value=0.0,
         format="%.2f",
         value=float(existing["amount"]) if existing.get("amount") and existing.get("amount") != 0.0 else None,
@@ -462,15 +462,13 @@ def dialog_load_custom_batch():
 
 def render_custom_batch_inline(global_idx, batch, cost_sliders, unit):
     """Render a single custom batch inside its resource-group expander."""
-    n_methods = len(batch["methods"])
     amount_val = float(batch["amount"])
-    batch["unit"] = unit  # keep in sync for Excel export
+    batch["unit"] = unit
 
-    # st.markdown(f"🆕 **{batch['name']}** — CDR methods: **{n_methods}**")
     with st.container(border=True):
         key_amount = f"custom_amount_{global_idx}"
         if key_amount not in st.session_state:
-            st.session_state[key_amount] = amount_val
+            st.session_state[key_amount] = amount_val if amount_val else None
 
         col_amount, _, _, _ = st.columns(4)
         with col_amount:
@@ -479,9 +477,11 @@ def render_custom_batch_inline(global_idx, batch, cost_sliders, unit):
                 min_value=0.0,
                 format="%.2f",
                 key=key_amount,
+                placeholder="0.0",
             )
-        if new_amount != amount_val:
-            st.session_state.custom_resources[global_idx]["amount"] = float(new_amount)
+        new_amount_float = float(new_amount) if new_amount is not None else 0.0
+        if new_amount_float != amount_val:
+            st.session_state.custom_resources[global_idx]["amount"] = new_amount_float
             st.session_state.pop("latest_result", None)
 
         col_min = f"Min ({unit}/MtCO₂)"
@@ -575,7 +575,8 @@ def render_tab(cost_sliders):
     st.markdown('<p class="objective_title">OBJECTIVE</p>', unsafe_allow_html=True)
     st.markdown(
         '<p class="text_with_border">This section lets you define the <strong>total available '
-        'quantities of each resource</strong> for the optimization model.</p>',
+        'quantities of each resource</strong> for the optimization model.<br>'
+        'Availability is per <strong>year</strong> (rate) for the specific year the portfolio is being estimated, for example 2030, or 2050</p>',
         unsafe_allow_html=True,
     )