Add English translations for all 379 recipe and tip files

Use dotlang AI translation (aiursoft-instruct:latest via Ollama) to
translate all Chinese content to English under en/ subfolder:
- en/dishes/: all recipe categories (aquatic, breakfast, condiment,
  dessert, drink, meat_dish, semi-finished, soup, staple, vegetable_dish)
- en/tips/: learn/ and advanced/ cooking guides
- en/README.md, en/CONTRIBUTING.md, en/CODE_OF_CONDUCT.md

The mkdocs-static-i18n plugin (docs_structure: folder) serves Chinese
at the root and English at /en/, with a language switcher in the UI.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

en/dishes/breakfast/温泉蛋/温泉蛋.md

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+# How to Make Onsen Tamago
+
+A traditional Japanese snack that can be used as a side dish. Note the distinction from soft-boiled eggs: in soft-boiled eggs, the white is cooked while the yolk remains runny; in onsen tamago, the white is runny while the yolk is cooked.
+
+Estimated Cooking Difficulty: ★★★
+
+## Essential Ingredients and Tools
+
+### Main Ingredients
+
+- Eggs
+
+### Essential Tools
+
+- Kitchen thermometer (preferably one with a clip)
+- Cup (no specific requirements; any cup will do)
+
+### Secondary Ingredients
+
+Optional ingredients for garnish
+
+- Kelp soy sauce (a low-salt Japanese soy sauce used for seasoning the onsen tamago)
+- Scallions
+
+## Quantities
+
+- Use 1 egg, adjusting the quantity based on your appetite and the size of your pot.
+
+## Instructions
+
+### Boiling the Eggs
+
+- Fill a pot with tap water, ensuring the water level is about 3 cm above the eggs. Insert a thermometer into the water.
+- Turn on the heat or the induction cooktop. Gradually adjust the power or flame size to maintain the water temperature at **70 degrees Celsius**.
+- Place the eggs in the pot. Do not stack the eggs on top of each other; they should all rest at the bottom with enough space to move around.
+- Maintain this temperature for **25 minutes**.
+- Prepare a bowl of ice water.
+- Remove the eggs and immediately place them in the ice water, **waiting for 3 minutes**.
+- Crack the eggs into a small bowl to complete the preparation.
+
+## Additional Content
+
+### Flowchart
+
+``` mermaid
+graph TD
+    A[锅中加水，插入温度计] --> B[控制水温到70℃]
+    B --> C[放入鸡蛋，保持水温为70℃ 25分钟]
+    B --> D[准备冰水]
+    C --> E
+    D --> E[鸡蛋捞出放入冰水，等待3分钟]
+    E --> F[鸡蛋打入小碗]
+```
+
+### Notes
+
+- If using a mechanical thermometer (which does not require power), the probe must be submerged in the water by at least 6 cm. If using an electronic thermometer, there are no special requirements.
+- A slightly thicker pot is recommended for better temperature control.
+- Although holding at 70°C for 25 minutes is sufficient to kill Salmonella, it is still advisable to consume fewer raw eggs or purchase pasteurized eggs specifically labeled as safe for raw consumption.
+
+If you encounter any issues or have suggestions for improving the process while following this guide, please submit an Issue or Pull request.