Add printer lifecycle fields and printer log

- Printer: bought_at, last_maintenance_at, decommissioned_at (all Date, nullable)
- PrinterLog: per-printer timestamped text entries (CASCADE delete)
- Migration 0003: adds columns + printer_logs table
- /printers/{id}: detail page showing lifecycle info + scrollable log
- POST /printers/{id}/log: add a log entry via modal form
- Printer names in list are now links to the detail page
- Add Printer modal includes optional purchase date

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

app/templates/printer_detail.html

@@ -0,0 +1,109 @@
+{% extends "base.html" %}
+{% block title %}{{ printer.name }} — POPS{% endblock %}
+
+{% block content %}
+<div class="d-flex align-items-center gap-3 mb-4">
+  <a href="/printers" class="text-secondary text-decoration-none"><i class="bi bi-arrow-left"></i></a>
+  <h5 class="text-white mb-0">{{ printer.name }}</h5>
+  {% set s = printer.status.value %}
+  {% if   s == 'printing' %}<span class="badge bg-primary">printing</span>
+  {% elif s == 'idle'     %}<span class="badge bg-success">idle</span>
+  {% elif s == 'error'    %}<span class="badge bg-danger">error</span>
+  {% else                 %}<span class="badge bg-secondary">offline</span>
+  {% endif %}
+  {% if printer.decommissioned_at %}
+  <span class="badge bg-warning text-dark">decommissioned</span>
+  {% endif %}
+</div>
+
+<div class="row g-3 mb-4">
+
+  {# ── Info card ── #}
+  <div class="col-md-6">
+    <div class="card h-100">
+      <div class="card-header text-secondary small text-uppercase fw-normal" style="border-color:#21262d">Details</div>
+      <div class="card-body">
+        <table class="table table-dark table-sm mb-0" style="font-size:.875rem">
+          <tbody>
+            <tr><td class="text-secondary border-0" style="width:40%">Type</td>
+                <td class="border-0">{{ printer.printer_type.name if printer.printer_type else '—' }}</td></tr>
+            <tr><td class="text-secondary">Bed volume</td>
+                <td>{% if printer.printer_type %}{{ printer.printer_type.bed_x_mm }}×{{ printer.printer_type.bed_y_mm }}×{{ printer.printer_type.bed_z_mm }} mm{% else %}—{% endif %}</td></tr>
+            <tr><td class="text-secondary">Location</td>
+                <td>{{ printer.location or '—' }}</td></tr>
+          </tbody>
+        </table>
+      </div>
+    </div>
+  </div>
+
+  {# ── Lifecycle card ── #}
+  <div class="col-md-6">
+    <div class="card h-100">
+      <div class="card-header text-secondary small text-uppercase fw-normal" style="border-color:#21262d">Lifecycle</div>
+      <div class="card-body">
+        <table class="table table-dark table-sm mb-0" style="font-size:.875rem">
+          <tbody>
+            <tr><td class="text-secondary border-0" style="width:50%">Purchased</td>
+                <td class="border-0">{{ printer.bought_at.strftime('%d.%m.%Y') if printer.bought_at else '—' }}</td></tr>
+            <tr><td class="text-secondary">Last maintenance</td>
+                <td>{{ printer.last_maintenance_at.strftime('%d.%m.%Y') if printer.last_maintenance_at else '—' }}</td></tr>
+            <tr><td class="text-secondary">Decommissioned</td>
+                <td>{{ printer.decommissioned_at.strftime('%d.%m.%Y') if printer.decommissioned_at else '—' }}</td></tr>
+          </tbody>
+        </table>
+      </div>
+    </div>
+  </div>
+
+</div>
+
+{# ── Log ── #}
+<div class="d-flex align-items-center justify-content-between mb-3">
+  <h6 class="text-white mb-0">Log</h6>
+  <button class="btn btn-sm btn-outline-primary" data-bs-toggle="modal" data-bs-target="#addLogModal">
+    <i class="bi bi-plus-lg me-1"></i>Add entry
+  </button>
+</div>
+
+<div class="card">
+  {% if printer.logs %}
+  <table class="table table-dark table-hover mb-0 align-middle">
+    <tbody>
+    {% for entry in printer.logs %}
+    <tr>
+      <td class="text-secondary small" style="width:140px;white-space:nowrap">
+        {{ entry.created_at.strftime('%d.%m.%Y %H:%M') }}
+      </td>
+      <td>{{ entry.message }}</td>
+    </tr>
+    {% endfor %}
+    </tbody>
+  </table>
+  {% else %}
+  <div class="card-body text-secondary">No log entries yet.</div>
+  {% endif %}
+</div>
+
+{# ── Add log entry modal ── #}
+<div class="modal fade" id="addLogModal" tabindex="-1">
+  <div class="modal-dialog">
+    <div class="modal-content bg-dark border-secondary">
+      <form method="POST" action="/printers/{{ printer.id }}/log">
+        <div class="modal-header border-secondary">
+          <h6 class="modal-title text-white">Add Log Entry</h6>
+          <button type="button" class="btn-close btn-close-white" data-bs-dismiss="modal"></button>
+        </div>
+        <div class="modal-body">
+          <textarea name="message" class="form-control bg-dark border-secondary text-white"
+                    rows="3" placeholder="What happened?" required autofocus></textarea>
+        </div>
+        <div class="modal-footer border-secondary">
+          <button type="button" class="btn btn-secondary btn-sm" data-bs-dismiss="modal">Cancel</button>
+          <button type="submit" class="btn btn-primary btn-sm">Add</button>
+        </div>
+      </form>
+    </div>
+  </div>
+</div>
+{% endblock %}