[ethan42]

Updates chapter 7 for the 2026-27 lecture 7 slides (assets/pdf/lec07.pdf on the course site). The new slides URL goes live when progintro.github.io#40 is merged.

The deck has 21 pages instead of 23:

• p. 2: the AWS outage is replaced by a PHP security flaw and the question «σε ποια γλώσσα είναι γραμμένος ο διερμηνέας της PHP;» (C).
• p. 3: the three GRCPC results pages (old pp. 3–5) became one empty announcements page. Every later page moves down by 2 (old pp. 6–23 → new pp. 4–21).
• p. 15: the filter loop for the product of the odd multiples of 7 now starts at i = 101, fixing the old i = 100.

Changes:

• Chapter 7:
  • §7.1 opens with the PHP example and keeps AWS as the 2025-26 example.
  • §7.2 (GRCPC) says it comes from the 2025-26 slides.
  • §7.12 shows the fixed loop and explains the 2025-26 version. The «Συχνά λάθη» item and exercise Ε7.3 about i = 100 stay, since they're still useful.
  • The reading list has the new page numbers and a link to the 2025-26 deck.
• Two slide questions: both point to the new deck. Their pages change 14 → 12 and 16 → 14.
• Other files: sources/extract/lec07.yaml (new outline and pointers, plus an issue describing the changes), the manifest, make fetch, and the README line «Διαλέξεις 0–7».

make check passes.

Opened from socrates.