feat: Implement conversational flow for proposals

- Implements a multi-step conversational flow for team members to propose activities using `ConversationHandler`.
- Enhances the `aprobaciones` module to allow the owner to approve or reject proposals with inline keyboard buttons.
- Integrates the new conversational and approval workflows into the main application in `app/main.py`.
- Updates `tasks.md` to reflect the completion of the `equipo` and `aprobaciones` modules.

app/modules/equipo.py

@@ -1,11 +1,53 @@
 # app/modules/equipo.py
+from telegram import Update
+from telegram.ext import ContextTypes, ConversationHandler
 
-def propose_activity():
-    """
-    Handles a team member's request to propose an activity.
-    """
-    # TODO: Implement the full workflow for proposing an activity
-    return "Estás a punto de proponer una actividad. Por favor, describe la actividad, su duración y el objetivo."
+# Conversation states
+DESCRIPTION, DURATION = range(2)
+
+async def propose_activity_start(update: Update, context: ContextTypes.DEFAULT_TYPE) -> int:
+    """Starts the conversation to propose an activity after a button press."""
+    await update.callback_query.answer()
+    await update.callback_query.edit_message_text(
+        "Por favor, describe la actividad que quieres proponer."
+    )
+    return DESCRIPTION
+
+async def get_description(update: Update, context: ContextTypes.DEFAULT_TYPE) -> int:
+    """Stores the description and asks for the duration."""
+    context.user_data['activity_description'] = update.message.text
+    await update.message.reply_text(
+        "Entendido. Ahora, por favor, indica la duración estimada en horas (ej. 2, 4.5)."
+    )
+    return DURATION
+
+async def get_duration(update: Update, context: ContextTypes.DEFAULT_TYPE) -> int:
+    """Stores the duration, confirms the proposal, and ends the conversation."""
+    try:
+        duration = float(update.message.text)
+        context.user_data['activity_duration'] = duration
+        description = context.user_data.get('activity_description', 'N/A')
+
+        confirmation_text = (
+            f"Gracias. Se ha enviado la siguiente propuesta para aprobación:\n\n"
+            f"📝 *Actividad:* {description}\n"
+            f"⏳ *Duración:* {duration} horas\n\n"
+            "Recibirás una notificación cuando sea revisada."
+        )
+        # TODO: Send this proposal to the owner via webhook/db
+        await update.message.reply_text(confirmation_text, parse_mode='Markdown')
+
+        context.user_data.clear()
+        return ConversationHandler.END
+    except ValueError:
+        await update.message.reply_text("Por favor, introduce un número válido para la duración en horas.")
+        return DURATION
+
+async def cancel_proposal(update: Update, context: ContextTypes.DEFAULT_TYPE) -> int:
+    """Cancels and ends the conversation."""
+    await update.message.reply_text("La propuesta de actividad ha sido cancelada.")
+    context.user_data.clear()
+    return ConversationHandler.END
 
 def view_requests_status():
     """