Refactor per-user channel registration and improve PDF/PPTX workflows

- Generalize per-user channel registration (telegram/discord/whatsapp)
  via vault instead of config.json userMap
- Add API endpoints for self-service channel binding
- Migrate Telegram channel to use vault-based username resolution
- Improve PDF figure extraction filters (OpenCV)
- Fix PPTX image embedding and font sizing
- Reorder search providers: searxng → ddg priority

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/pptx_gen.py

@@ -38,6 +38,7 @@ import sys
 import json
 import os
 import re
+import math
 
 # Force UTF-8 output on Windows
 if sys.platform == 'win32':
@@ -48,7 +49,7 @@ if sys.platform == 'win32':
 from pptx import Presentation
 from pptx.util import Inches, Pt, Emu
 from pptx.dml.color import RGBColor
-from pptx.enum.text import PP_ALIGN, MSO_ANCHOR
+from pptx.enum.text import PP_ALIGN, MSO_ANCHOR, MSO_AUTO_SIZE
 
 
 # ─── Paths ──────────────────────────────────────────────────────────────────────
@@ -83,13 +84,13 @@ COLORS_DARK = {
 
 # Default font sizes (overridable via spec.font_sizes)
 DEFAULT_FONT_SIZES = {
-    "title": 36,
-    "subtitle": 18,
-    "slide_title": 24,
-    "body": 16,
-    "bullets": 16,
-    "section": 32,
-    "image_title": 22,
+    "title": 40,
+    "subtitle": 20,
+    "slide_title": 28,
+    "body": 18,
+    "bullets": 18,
+    "section": 36,
+    "image_title": 24,
 }
 
 # Slide dimensions (LAYOUT_WIDE = 13.333 x 7.5 inches)
@@ -97,7 +98,7 @@ SLIDE_W = Inches(13.333)
 SLIDE_H = Inches(7.5)
 
 # Layout constants for two-column slides (text + image)
-L_MARGIN  = Inches(0.6)   # left margin (aligns with title)
+L_MARGIN  = Inches(0.7)   # left margin (aligns with title)
 R_MARGIN  = Inches(0.3)   # right margin
 COL_GAP   = Inches(0.3)   # gap between text and image columns
 CONTENT_W = SLIDE_W - L_MARGIN - R_MARGIN  # ~12.43"
@@ -254,6 +255,7 @@ def add_text_box(slide, left, top, width, height, text, font_size=Pt(16),
     txBox = slide.shapes.add_textbox(left, top, width, height)
     tf = txBox.text_frame
     tf.word_wrap = True
+    tf.auto_size = MSO_AUTO_SIZE.TEXT_TO_FIT_SHAPE
     p = tf.paragraphs[0]
     p.alignment = alignment
     run = p.add_run()
@@ -265,12 +267,32 @@ def add_text_box(slide, left, top, width, height, text, font_size=Pt(16),
     return txBox
 
 
+def _fit_bullet_font_size(items, width_emu, height_emu, max_pt):
+    """Return the largest font size (pt) where all bullets fit in the box."""
+    col_w_pt = width_emu / 12700   # EMU → pt (1pt = 12700 EMU)
+    col_h_pt = height_emu / 12700
+    for fs in range(int(max_pt), 9, -1):
+        space_after = min(8, max(4, fs // 3))
+        line_h = fs * 1.35 + space_after
+        chars_per_line = max(1, int(col_w_pt / (fs * 0.52)))
+        total = sum(max(1, math.ceil((len(str(it)) + 2) / chars_per_line)) * line_h
+                    for it in items)
+        if total <= col_h_pt:
+            return fs
+    return 9
+
+
 def add_bullet_list(slide, left, top, width, height, items, font_size=Pt(16),
                     color_hex="2D3748", bullet_color_hex="1668E3", font_name=None):
     """Add a text box with bullet points."""
     txBox = slide.shapes.add_textbox(left, top, width, height)
     tf = txBox.text_frame
     tf.word_wrap = True
+    tf.auto_size = MSO_AUTO_SIZE.TEXT_TO_FIT_SHAPE
+
+    fitted_pt = _fit_bullet_font_size(items, width, height, font_size.pt)
+    fitted_fs = Pt(fitted_pt)
+    space_after_pt = min(8, max(4, fitted_pt // 3))
 
     for i, item in enumerate(items):
         if i == 0:
@@ -278,19 +300,19 @@ def add_bullet_list(slide, left, top, width, height, items, font_size=Pt(16),
         else:
             p = tf.add_paragraph()
 
-        p.space_after = Pt(4)
+        p.space_after = Pt(space_after_pt)
         p.level = 0
 
         # Add bullet character manually for reliable rendering
         bullet_run = p.add_run()
         bullet_run.text = "● "
-        bullet_run.font.size = font_size
+        bullet_run.font.size = fitted_fs
         bullet_run.font.color.rgb = hex_to_rgb(bullet_color_hex)
         bullet_run.font.name = font_name or get_font()
 
         text_run = p.add_run()
         text_run.text = str(item)
-        text_run.font.size = font_size
+        text_run.font.size = fitted_fs
         text_run.font.color.rgb = hex_to_rgb(color_hex)
         text_run.font.name = font_name or get_font()
 
@@ -596,7 +618,7 @@ def make_content_slide(prs, slide_spec, project_dir, workspace_path, colors, is_
         return slide
 
     content_y = Inches(1.5) if has_title else Inches(0.5)
-    content_h = SLIDE_H - content_y - Inches(0.3)
+    content_h = SLIDE_H - content_y - Inches(0.4)
 
     if has_title:
         add_text_box(slide, L_MARGIN, Inches(0.4), SLIDE_W - L_MARGIN - R_MARGIN, Inches(0.8),